ORCID Profile
0000-0003-0713-4864
Current Organisation
The University of Manitoba
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Publisher: American Physical Society (APS)
Date: 02-10-2006
Publisher: IEEE
Date: 09-2015
Publisher: IOP Publishing
Date: 07-06-1993
Publisher: Elsevier BV
Date: 05-2010
Publisher: IOP Publishing
Date: 15-07-1997
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2013
Publisher: IOP Publishing
Date: 29-09-2016
Publisher: IOP Publishing
Date: 05-2006
Publisher: American Physical Society (APS)
Date: 27-02-2014
Publisher: American Physical Society (APS)
Date: 15-11-2004
Publisher: AIP Publishing
Date: 22-10-2001
DOI: 10.1063/1.1413731
Abstract: The influence of local defects in exchange biased ferromagnetic/antiferromagnetic bilayers is studied using numerical simulations. The location of defects relative to the interface is found to be the main factor determining the magnitude of coercive and bias field modifications. One consequence is that some types of defects control stability of partial wall structures. This may explain coercivity enhancement as arising from irreversible pinning of partial domain walls in the antiferromagnet.
Publisher: American Physical Society (APS)
Date: 17-01-2012
Publisher: American Physical Society (APS)
Date: 12-2006
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2011
Publisher: American Physical Society (APS)
Date: 07-1989
Publisher: Elsevier BV
Date: 04-2002
Publisher: AIP Publishing
Date: 09-05-2003
DOI: 10.1063/1.1558244
Abstract: The ferromagnetic resonance frequencies have been calculated for a soft/hard Co/CoPt exchange spring thin film system. In this geometry the magnetostatics are crucial to understanding the variation of resonant frequency with field due to the out-of-plane component of magnetization of the CoPt hard layer. When exchange coupling between films exists, significant changes in the resonant frequency occur. For in-plane reverse applied fields, a spiral is formed in the soft Co layer. This appears as a double minimum in the resonant frequency as a function of the in-plane applied field. The positions of the frequency minima correspond to the beginning and end of the spiral formation in the Co layer. The frequency of the maximum provides a sensitive measure of the perpendicular anisotropy in the cobalt film.
Publisher: AIP Publishing
Date: 25-05-2004
DOI: 10.1063/1.1687552
Abstract: Epitaxial Fe/KFeF3 bilayers were grown using molecular beam epitaxy on GaAs (100). FMR measurements revealed two peaks for s les with an Fe seed layer. A peak with fourfold symmetry was identified as the main layer Fe whereas a peak with twofold symmetry appeared to be due to the seed layer Fe. The magnetocrystalline anisotropy for the fourfold peak is ∼400 Oe at 300 K whereas a large anisotropy of 1.5 kOe is associated with the seed layer. A large rotatable anisotropy of 280±20 Oe was found for a s le with Fe thickness 2.1 nm. All Fe/KFeF3 bilayers checked by superconducting quantum interference device exhibit exchange bias and enhanced coercivity. The blocking temperature of the system is close to the Néel temperature 112 K of KFeF3. One s le has polycrystalline KFeF3 and shows a much larger exchange bias and coercivity than the s les having single crystal KFeF3.
Publisher: AIP Publishing
Date: 19-12-2011
DOI: 10.1063/1.3671392
Abstract: Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1−xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of ∼1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.
Publisher: American Chemical Society (ACS)
Date: 24-08-2016
Publisher: IOP Publishing
Date: 26-09-2011
DOI: 10.1088/0022-3727/44/41/415003
Abstract: Results from ferromagnetic resonance experiments carried out on epitaxially grown Fe/KNiF 3 /FeF 2 trilayers are presented. Exchange coupling between the KNiF 3 , a weak anisotropy antiferromagnet, and the Fe leads to shifts in the resonance field of the ferromagnet. The field shifts can be described by a temperature-dependent exchange anisotropy . depends on the orientation direction of the applied field relative to the magnetic anisotropy axis, and a non-monotonic dependence on KNiF 3 thickness. Three thickness regimes appear that correspond to different values of exchange bias in each region. A qualitative understanding of the basis for these three thickness regimes due to spin canting at the interfaces is presented. Our results illustrate a method to tune the value of exchange anisotropy using a combination of different antiferromagnets.
Publisher: AIP Publishing
Date: 06-2001
DOI: 10.1063/1.1359469
Abstract: Some models for exchange bias at the interface of a ferromagnet and antiferromagnet involve the formation of partial domain walls in the antiferromagnet layer. Numerical calculations of mean-field temperature dependence are used to examine thermally induced instabilities in the partial domain wall at ideal compensated and uncompensated antiferromagnet interfaces. At compensated interfaces, depinning of the partial wall results in a total loss of bias. At uncompensated interfaces, thermal effects at the interface cause the wall to move into the antiferromagnet. The critical fields for this partial depinning are different for the forward and reverse magnetization directions. This mechanism on uncompensated interfaces allows for simultaneous loop shift and coercivity, which is not found in the compensated case.
Publisher: Elsevier BV
Date: 04-1996
Publisher: American Physical Society (APS)
Date: 14-03-2017
Publisher: American Physical Society (APS)
Date: 18-01-2017
Publisher: American Physical Society (APS)
Date: 18-06-2015
Publisher: Elsevier BV
Date: 05-2004
Publisher: American Physical Society (APS)
Date: 02-1987
Publisher: IOP Publishing
Date: 28-11-2014
Publisher: American Physical Society (APS)
Date: 13-08-2007
Publisher: AIP Publishing
Date: 06-2001
DOI: 10.1063/1.1359477
Abstract: The exchange bias effect is known to depend strongly on the condition of the ferromagnet/antiferromagnet interface. Bilayers of single-crystal Fe and polycrystalline KNiF3 were grown and exchange bias observed using superconducting quantum interference device magnetometry. Hysteresis loops after field cooling are asymmetric in the forward and reverse directions. This asymmetry disappears at 50 K, indicating a blocking temperature for the bias well below the Néel temperature of KNiF3 (250 K).
Publisher: American Physical Society (APS)
Date: 09-12-2014
Publisher: American Physical Society (APS)
Date: 28-06-2010
Publisher: American Physical Society (APS)
Date: 15-04-1985
Publisher: AIP Publishing
Date: 04-1994
DOI: 10.1063/1.356092
Abstract: Brillouin light scattering (BLS) in the backscattering configuration has been used to study the magnetic excitations in epitaxial Fe(38 Å)/Cr(13 Å)/Fe(38 Å) thin-film sandwiches. Spin-wave frequency was measured versus in-plane wave vector k and static in-plane magnetic field H for both [100] and [110] direction fields and with k perpendicular to H. The range of applied fields was 50–1500 Oe. The wave-number range was 0.45×105–2.3×105 rad/cm. The BLS spectra correlate with magnetization versus field profiles and confirm the antiferromagnetic coupling between the Fe layers. Under low-field conditions and near-antiparallel alignment of the Fe layer magnetization vectors, the spin-wave frequencies from the Stokes and anti-Stokes sides of the BLS spectra are different. These frequencies merge at high field. The low-field splitting feature is very sensitive to small differences in thickness for the magnetic layers and indicates a thickness difference of 9%. Matchups between features of the BLS data and magnetization curves were obtained for the following parameters: magnetic layer saturation induction 4πMs=18.6 kG cubic anisotropy field HA=550 Oe in-plane [110] uniaxial anisotropy field HU=76 Oe antiferromagnetic interlayer exchange coupling field HJ=120 Oe. Spin-wave frequency calculations based on these parameters show quantitative agreement with the measurements. The quantitative fits require inclusion in the theory of an iron layer surface anisotropy with an effective surface anisotropy field of 2 kOe.
Publisher: Springer Science and Business Media LLC
Date: 20-01-2020
Publisher: Elsevier BV
Date: 02-2005
Publisher: Elsevier BV
Date: 03-1993
Publisher: American Physical Society (APS)
Date: 16-05-2007
Publisher: The Optical Society
Date: 07-11-2014
DOI: 10.1364/OE.22.028467
Publisher: American Physical Society (APS)
Date: 27-05-2005
Publisher: IOP Publishing
Date: 18-07-2014
Publisher: AIP Publishing
Date: 24-11-2015
DOI: 10.1063/1.4936199
Abstract: We report the static and dynamic magnetic characteristics of a high-layer-number NiFe/FeMn multilayer test structure with potential applications in broadband absorber and filter devices. To allow fine control over the absorption linewidths and to understand the mechanisms governing the resonances in a tailored structure similar to that expected to be used in real world applications, the multilayer was intentionally designed to have layer thickness and interface roughness variations. Magnetometry measurements show that the s le has complex hysteresis loops with features consistent with single ferromagnetic film reversals. Characterisation by transmission electron microscopy allows us to correlate the magnetic properties with structural features, including the film widths and interface roughnesses. Analysis of resonance frequencies from broadband ferromagnetic resonance measurements as a function of field magnitude and orientation provide values of the local exchange bias, rotatable anisotropy, and uniaxial anisotropy fields for specific layers in the stack and explain the observed mode softening. The linewidths of the multilayer are adjustable around the bias field, approaching twice that seen at larger fields, allowing control over the bandwidth of devices formed from the structure.
Publisher: American Physical Society (APS)
Date: 15-03-2012
Publisher: American Physical Society (APS)
Date: 29-03-2017
Publisher: American Chemical Society (ACS)
Date: 18-03-2008
DOI: 10.1021/JP8009113
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2008
Publisher: IOP Publishing
Date: 30-07-2014
Publisher: American Physical Society (APS)
Date: 29-04-2004
Publisher: American Physical Society (APS)
Date: 29-04-2004
Publisher: AIP Publishing
Date: 06-2001
DOI: 10.1063/1.1357867
Abstract: Long-wavelength spin waves are examined in an exchange biased ferromagnet/antiferromagnet bilayer. The frequencies of the excitations are calculated as a function of external field strength and orientation. It is suggested that the angular dependence of the frequencies can lead to linewidth enhancements, in agreement with recent experimental results. It is also shown that the study of the spin wave frequencies can yield the strengths of the antiferromagnet anisotropy and interlayer coupling.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2005
Publisher: American Physical Society (APS)
Date: 11-1994
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2000
DOI: 10.1109/20.908725
Publisher: Elsevier BV
Date: 10-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2010
Publisher: AIP Publishing
Date: 28-12-2014
DOI: 10.1063/1.4904857
Abstract: By using the stripline Microwave Vector–Network Analyser Ferromagnetic Resonance and Time Domain spectroscopy techniques, we study a strong coupling regime of magnons to microwave photons in the planar geometry of a lithographically formed split-ring resonator (SRR) loaded by a single-crystal epitaxial yttrium–iron–garnet (YIG) film. Strong anti-crossing of the photon modes of SRR and of the magnon modes of the YIG film is observed in the applied-magnetic-field resolved measurements. The coupling strength extracted from the experimental data reaches 9% at 3 GHz. Theoretically, we propose an equivalent circuit model of the SRR loaded by a magnetic film. This model follows from the results of our numerical simulations of the microwave field structure of the SRR and of the magnetisation dynamics in the YIG film driven by the microwave currents in the SRR. The results obtained with the equivalent-circuit model are in good agreement with the experiment. This model provides a simple physical explanation of the process of mode anti-crossing. Our findings are important for future applications in microwave quantum photonic devices as well as in nonlinear and magnetically tuneable metamaterials exploiting the strong coupling of magnons to microwave photons.
Publisher: American Physical Society (APS)
Date: 15-08-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-1998
DOI: 10.1109/20.706364
Publisher: American Physical Society (APS)
Date: 09-06-2010
Publisher: American Physical Society (APS)
Date: 11-1992
Publisher: American Physical Society (APS)
Date: 15-11-2007
Publisher: American Physical Society (APS)
Date: 25-05-2006
Publisher: American Physical Society (APS)
Date: 16-03-2017
Publisher: American Physical Society (APS)
Date: 03-01-2006
Publisher: AIP Publishing
Date: 21-03-2003
DOI: 10.1063/1.1558203
Abstract: Polarization reversal in ferroelectric particles driven by a pulsed electric field is examined theoretically using Landau–Devonshire–Khalatnikov theory. A significant reduction in reversal times is shown to be possible if certain surface properties and size criteria are met. The surface properties are also shown to control the magnitude of the applied field needed for irreversible switching. An interesting signature of surface effects is found in the switching current. The theory predicts that the switching current for small ferroelectric particles can exhibit double peaks as a function of time. The size and relative times of the peaks provide specific information on the magnitude and rate of surface reversal dynamics.
Publisher: AIP Publishing
Date: 06-2015
DOI: 10.1063/1.4922055
Abstract: We explore an emerging device concept based on exchange bias used in conjunction with an antidot geometry to fine tune ferromagnetic resonances. Planar cavity ferromagnetic resonance is used to study the microwave response of NiO/NiFe bilayers with antidot structuring. A large frequency asymmetry with respect to an applied magnetic field is found across a broad field range whose underlying cause is linked to the distribution of magnetic poles at the antidot surfaces. This distribution is found to be particularly sensitive to the effects of exchange bias, and robust in regards to the quality of the antidot geometry. The template based antidot geometry we study offers advantages for practical device construction, and we show that it is suitable for broadband absorption and filtering applications, allowing tunable anisotropies via interface engineering.
Publisher: IOP Publishing
Date: 10-04-2012
Publisher: American Physical Society (APS)
Date: 10-1995
Publisher: American Physical Society (APS)
Date: 09-1991
Publisher: Elsevier BV
Date: 04-2005
Publisher: IEEE
Date: 2005
Publisher: Elsevier BV
Date: 02-2005
Publisher: IOP Publishing
Date: 07-2008
Publisher: American Physical Society (APS)
Date: 15-08-2016
Publisher: Springer Science and Business Media LLC
Date: 03-2006
Publisher: American Physical Society (APS)
Date: 05-1993
Publisher: American Physical Society (APS)
Date: 12-1993
Publisher: American Physical Society (APS)
Date: 08-02-2011
Publisher: American Physical Society (APS)
Date: 11-1992
Publisher: American Physical Society (APS)
Date: 06-03-2008
Publisher: AIP Publishing
Date: 06-2001
DOI: 10.1063/1.1359790
Abstract: Fast reversal processes in magnetic particles and arrays involve fundamental magnetic dynamic and relaxation processes. Exchange and dipolar interactions determine equilibrium ground states and strongly influence linear and nonlinear dynamics. Calculations are used to show how high frequency resonances in arrays of densely packed magnetic particles can affect reversal times, possibly leading to dramatic decreases in switching rates. High frequency excitations and dynamic processes in interface exchange coupled magnets are also discussed, with emphasis on exchange biased materials. The exchange bias effect is closely related to interface magnetic structure and magnetization processes in systems of ferromagnets exchange coupled to antiferromagnets. It is shown how magnetization processes in the antiferromagnet can be studied through observation of dynamic effects in the ferromagnetic component.
Publisher: American Physical Society (APS)
Date: 19-02-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1999
DOI: 10.1109/20.800498
Publisher: Elsevier BV
Date: 06-2006
Publisher: American Physical Society (APS)
Date: 09-1992
Publisher: American Physical Society (APS)
Date: 09-2006
Publisher: MIT Press - Journals
Date: 02-2006
DOI: 10.1162/089976606775093891
Abstract: Slightly modified versions of an early Hebbian/anti-Hebbian neural network are shown to be capable of extracting the sparse, independent linear components of a prefiltered natural image set. An explanation for this capability in terms of a coupling between two hypothetical networks is presented. The simple networks presented here provide alternative, biologically plausible mechanisms for sparse, factorial coding in early primate vision.
Publisher: American Physical Society (APS)
Date: 06-12-2011
Publisher: IOP Publishing
Date: 25-10-2012
Publisher: AIP Publishing
Date: 08-2013
DOI: 10.1063/1.4818002
Abstract: Observation of an unusual, negatively-charged antiphase boundary in (Bi0.85Nd0.15)(Ti0.1Fe0.9)O3 is reported. Aberration corrected scanning transmission electron microscopy is used to establish the full three dimensional structure of this boundary including O-ion positions to ∼±10 pm. The charged antiphase boundary stabilises tetragonally distorted regions with a strong polar ordering to either side of the boundary, with a characteristic length scale determined by the excess charge trapped at the boundary. Far away from the boundary the crystal relaxes into the well-known Nd-stabilised antiferroelectric phase.
Publisher: AIP Publishing
Date: 18-09-2014
DOI: 10.1063/1.4895984
Abstract: Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs in the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.
Publisher: AIP Publishing
Date: 15-12-1984
DOI: 10.1063/1.333915
Abstract: We discuss antiferromagnetic bulk and surface spin waves, in the long wavelength region, on a finite thickness slab geometry. Implicit dispersion relations for both surface and bulk modes are derived, along with numerical calculations for MnF2 and GdAlO3. We find that the application of a magnetic field strongly localizes the surface spin wave to either the top or bottom surface of the film.
Publisher: Informa UK Limited
Date: 09-1994
Publisher: American Physical Society (APS)
Date: 17-09-2010
Publisher: IOP Publishing
Date: 18-02-2011
DOI: 10.1088/0953-8984/23/10/105901
Abstract: We present a theory for surface polaritons on ferroelectric-antiferromagnetic materials with canted spin structure. A small uniform canted moment is allowed, resulting in a weak ferromagnetism directed in the plane parallel to the surface. Surface and bulk polariton modes for a semi-infinite film are calculated for the case of transverse electric (TE) and transverse magnetic (TM) polarization. Ex le results are presented using parameters appropriate for BaMnF(4). We find that the surface modes are non-reciprocal for the TE polarization due to the magnetoelectric interaction, and the non-reciprocity can be controlled by an applied electric field. Ex le results for attenuated total reflection (ATR) are calculated. The magnetoelectric interaction also gives rise to 'leaky' surface modes in the case of TM polarization. These are pseudo-surface waves that exist in the pass band, and dissipate energy into the bulk of the material. We show that these pseudo-surface mode frequencies and properties can be modified by temperature and the application of external electric or magnetic fields.
Publisher: AIP Publishing
Date: 10-2010
DOI: 10.1063/1.3488618
Abstract: Broadband ferromagnetic resonance responses for metallic single-layer and bilayer magnetic films with total thicknesses smaller than the microwave magnetic skin depth have been studied. Two different types of microwave stripline transducers were used to excite and detect magnetization precession: a coplanar waveguide and a microstrip line both with characteristic width larger than the free propagation path for traveling spin waves along the film. Both transducers show efficient excitation of higher-order standing spin wave modes across the film thickness in s les 30–91 nm thick. The ratio of litudes of the first standing spin wave to the fundamental resonant mode is independent of frequency for single-layer permalloy films. In contrast, we find a strong variation in the litudes with frequency for cobalt–Permalloy bilayers and the ratio is strongly dependent on the ordering of layers with respect to a stripline transducer. Most importantly, cavity ferromagnetic resonance measurements on the same s les show considerably weaker litudes for the standing spin waves. All experimental data are consistent with expected effects of eddy currents in films with thicknesses below the microwave magnetic skin depth. Finally, conditions for observing eddy current effects in different types of experiments are critically examined.
Publisher: American Physical Society (APS)
Date: 1994
Publisher: AIP Publishing
Date: 07-05-2014
DOI: 10.1063/1.4862844
Publisher: American Physical Society (APS)
Date: 12-09-2011
Publisher: AIP Publishing
Date: 12-05-2005
DOI: 10.1063/1.1853932
Abstract: Results from magnetic viscosity experiments on chemically synthesized magnetic nanoparticles are presented. Our synthesized Fe20Pt80 particles are distinguished by a narrow size distribution but display features associated with broad distributions of activation rates. Results are presented from viscosity measurements in which the remnant magnetization is measured at different times after the removal of a static field, and studied as a function of temperature. We discuss how these results may be analyzed in terms of activation rate distributions for thermal activated reversal processes after the application and removal of a field. A method for the extraction of energy barrier distributions from directly measured time dependent data is presented.
Publisher: IOP Publishing
Date: 20-03-2012
Publisher: IOP Publishing
Date: 07-2006
Publisher: American Physical Society (APS)
Date: 19-04-2006
Publisher: American Physical Society (APS)
Date: 26-09-2011
Publisher: AIP Publishing
Date: 14-01-2008
DOI: 10.1063/1.2834714
Abstract: We demonstrate the functionality of spin-wave logic exclusive-not-OR and not-AND gates based on a Mach-Zehnder-type interferometer which has arms implemented as sections of ferrite film spin-wave waveguides. Logical input signals are applied to the gates by varying either the phase or the litude of the spin waves in the interferometer arms. This phase or litude variation is produced by Oersted fields of dc current pulses through conductors placed on the surface of the magnetic films.
Publisher: Springer Science and Business Media LLC
Date: 17-12-2006
DOI: 10.1038/NMAT1809
Abstract: Exchange bias is commonly manifested as the hysteresis-loop shift observed when a ferromagnet is in contact with an antiferromagnet. Here, we report observations of exchange bias with unusual features of a ferromagnet in contact with a spin glass, demonstrating that this is a phenomenon of greater generality. The easily measured properties of the ferromagnet allow access to the internal magnetic degrees of freedom of the glass to which they are coupled. Our results show that a Co/CuMn bilayer system exhibits all the rich phenomena of coercivity enhancement, bias-field shifts and training effects associated with a conventional ferromagnet/antiferromagnet system. Nevertheless, striking differences arise, such as an orientation reversal of the bias field in a small temperature range just below the blocking temperature. We argue that all features can be understood within the context of a random-field model for long-ranged oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) coupled spins.
Publisher: AIP Publishing
Date: 09-05-2003
DOI: 10.1063/1.1558653
Abstract: Exchange bias was studied in the Fe/KCoF3 ferromagnet/antiferromagnet system. KCoF3 can be deposited onto single crystal of Fe, either in the polycrystalline or single crystal form, depending on growth conditions. The s les were grown by molecular beam epitaxy on Ga-terminated GaAs (100) wafers. We study effects of the crystal state of the fluoride, thickness of the Fe film, crystallographic orientation of the Fe, and temperature on exchange bias. The structures with single crystal KCoF3 show that the exchange bias is well correlated with the coercivity at low temperatures and vanishes at a temperature close to the Néel temperature. Both the magnitude of the exchange bias and the blocking temperature of the s les with the polycrystalline fluoride were significantly reduced compared to the single crystal structures. As the Fe film thickness was increased, the exchange bias decreased for all s les. In contrast, the blocking temperature remained unchanged for the s les with the single-crystal fluoride. The exchange bias measured along the easy anisotropy axis of the Fe was slightly larger than that measured along the hard axis. In addition, all s les exhibited a weak training effect.
Publisher: IEEE
Date: 2002
Publisher: American Physical Society (APS)
Date: 18-08-2010
Publisher: Elsevier BV
Date: 02-2002
Publisher: American Physical Society (APS)
Date: 02-1993
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B9NJ00626E
Publisher: AIP Publishing
Date: 29-04-2004
DOI: 10.1063/1.1745112
Abstract: An alternative mechanism for exchange bias for ferromagnet/antiferromagnet bilayers with completely compensated interfaces is proposed and analyzed within the biquadratic coupling model. We show that a distribution of anisotropies in the antiferromagnet can lead to the appearance of exchange bias in a bilayer with a perfectly compensated interface without defects. The energy associated with the unidirectional anisotropy that gives rise to the shifted hysteresis curve is stored in antiferromagnetic domain walls between regions in the antiferromagnet with different anisotropy. This mechanism also leads naturally to an enhanced coercivity of the ferromagnet which is caused by the anisotropy in the antiferromagnet.
Publisher: American Physical Society (APS)
Date: 04-11-2016
Publisher: Elsevier BV
Date: 12-2007
Publisher: American Physical Society (APS)
Date: 10-08-2011
Publisher: American Physical Society (APS)
Date: 18-05-2007
Publisher: Elsevier BV
Date: 12-2007
Publisher: Elsevier BV
Date: 11-2008
Publisher: American Physical Society (APS)
Date: 16-05-2013
Publisher: Elsevier BV
Date: 02-1986
Publisher: IOP Publishing
Date: 07-05-2013
Publisher: AIP Publishing
Date: 28-04-2005
DOI: 10.1063/1.1849551
Abstract: The resonance frequencies of a cobalt (100nm)/Permalloy (50nm) exchange spring bilayer have been measured using a pulsed inductive microwave magnetometer. Two field dependent frequencies are detected which vary in relative intensity as a function of applied magnetic field. The two frequencies are identified as the optic and acoustic spin wave modes of coupled ferromagnetic films. Only over a limited range of fields are both frequencies observable. In low fields the acoustic mode is dominant, and in higher fields the optic mode gives the largest intensity. These intensity variations are explained in terms of off-resonant driving of cobalt modes by the uniform mode in Permalloy and a field dependent interfacial pinning.
Publisher: AIP Publishing
Date: 05-2012
DOI: 10.1063/1.4712033
Abstract: A numerical implementation of the transition state theory is presented which can be used to calculate the attempt frequency f0 of arbitrary shaped magnetic nanostructures. The micromagnetic equations are discretized using the finite element method. The climbing image nudged elastic band method is used to calculate the saddle point configuration, which is required for the calculation of f0. Excellent agreement of the implemented numerical model and analytical solutions is obtained for single domain particles. The developed method is applied to compare f0 for single phase and graded media grains of advanced recording media. f0 is predicted to be comparable if the maximum anisotropy is the same in these two media types.
Publisher: Elsevier BV
Date: 05-2004
Publisher: IOP Publishing
Date: 05-12-2009
DOI: 10.1088/0957-4484/20/1/015304
Abstract: We report on the control of magnetization reversal in exchange-biased Co/CoO nanorings resulting from the competition between field-cooling-induced unidirectional anisotropy at the Co/CoO interface and shape anisotropy of the elongated Co nanorings. We observed that the magnetization reversal mechanisms and magnitudes of exchange bias fields are strongly dependent on the strength and orientation of the cooling field relative to the major axis of the nanorings. Our results demonstrate a convenient technique to control the magnetization reversal modes in ferromagnetic nanorings.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2012
Publisher: AIP Publishing
Date: 27-06-2011
DOI: 10.1063/1.3606556
Abstract: We show that magnetic spin wave resonance modes in an antidot patterned array are sensitive to small changes in the magnetic configuration near dots, resulting in strong localization effects as the field is increased. Frequencies measured using ferromagnetic resonance from an antidot array patterned from a NiFe/IrMn bilayer are interpreted using micromagnetic calculations, and it is shown that the observed field dependence of the resonance response can be attributed to strong interdot localization of spin waves. This field tunable localization is created by stray fields produced by magnetic poles at the dot surfaces.
Publisher: American Physical Society (APS)
Date: 09-03-2005
Publisher: American Physical Society (APS)
Date: 04-02-2010
Publisher: American Physical Society (APS)
Date: 10-01-2006
Publisher: AIP Publishing
Date: 14-02-2012
DOI: 10.1063/1.3671434
Abstract: The field-induced dynamics of artificial spin ice are determined in part by interactions between magnetic islands and the switching characteristics of each island. Disorder in either of these affects the response to applied fields. Numerical simulations are used to show that disorder effects are determined primarily by the strength of disorder relative to inter-island interactions, rather than by the type of disorder. Weak and strong disorder regimes exist and can be defined in a quantitative way.
Publisher: American Physical Society (APS)
Date: 13-06-2014
Publisher: AIP Publishing
Date: 15-04-1991
DOI: 10.1063/1.347897
Abstract: The frequencies of long-wavelength spin wave modes are calculated for single and multilayer structures composed of ferromagnetic films with strong out-of-plane surface and interface anisotropies. The properties of these modes are examined from the point of view of possible Brillouin light-scattering studies and the evaluation of exchange constants and interface anisotropies. The frequencies of the collective modes on multilayer structures as well as their degree of localization to the surface of the stack are strongly affected by perpendicular anisotropies. This is demonstrated by studying the spectral density function obtained from an effective medium theory for semi-infinite superlattices.
Publisher: Wiley
Date: 16-12-2015
Publisher: AIP Publishing
Date: 2007
DOI: 10.1063/1.2426970
Abstract: Lateral quantization of an excitation in a confined geometry is shown to lead to multiple cutoff thresholds for parametric processes. This idea is illustrated with a calculation of parallel pump instability thresholds for a ferromagnetic metallic stripe. The lateral quantization by the strip geometry results in thresholds which change discontinuously with increasing stripe width. Magnetostatic interactions create a secondary fine structure of kinks on the threshold curve. This effect should be possible to detect experimentally and be used for precise measurement of microwave losses in patterned magnetic metals.
Publisher: AIP Publishing
Date: 28-12-2009
DOI: 10.1063/1.3279138
Abstract: Transmission of microwave spin waves through a microstructured magnonic crystal in the form of a Permalloy waveguide of a periodically varying width was studied experimentally and theoretically. The spin wave characteristics were measured by spatially resolved Brillouin light scattering microscopy. A rejection frequency band was clearly observed. The band gap frequency was controlled by the applied magnetic field. The measured spin-wave intensity as a function of frequency and propagation distance is in good agreement with a model calculation.
Publisher: IOP Publishing
Date: 20-01-2005
Publisher: Elsevier BV
Date: 06-1994
Publisher: American Physical Society (APS)
Date: 21-07-2005
Publisher: IOP Publishing
Date: 04-2010
Publisher: American Physical Society (APS)
Date: 21-11-2007
Publisher: American Physical Society (APS)
Date: 15-07-2011
Publisher: American Physical Society (APS)
Date: 25-01-2006
Publisher: AIP Publishing
Date: 15-02-2008
DOI: 10.1063/1.2831792
Abstract: The spectrum of spin wave excitations on a nanometric two-dimensional periodical array of circular holes in a magnetic film was measured using the Brillouin light scattering technique. Two modes with positive group velocity in the frequency range between 4 and 7GHz were observed. Our calculations show that these correspond to the two lowest modes propagating along the edges of an effective stripe waveguide, perpendicular to the applied field, whose width is equal to the interhole distance. Moreover, a number of higher-frequency modes has been measured and identified as volume excitations of the same effective stripe.
Publisher: American Physical Society (APS)
Date: 02-05-2006
Publisher: AIP Publishing
Date: 09-05-2003
DOI: 10.1063/1.1557654
Abstract: A rate dependence of the magnetic domain structure has been observed in a Pt/Co multilayer. The form of the domain structure as a function of the rate of change of magnetization was studied using nanosecond pulsed magnetic fields. At low fields the magnetization pattern consists of a dendritic like growth of the domains. As the magnitude of the pulse field is increased the patterns change to a more circular structure with smooth boundaries. The change in structure can be quantified and is discussed in terms of a field dependence where different behaviors can be clearly identified. The structure observed results from a narrowing of the distribution of energy barriers to reversal as the field is increased.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1995
DOI: 10.1109/20.489818
Publisher: Elsevier BV
Date: 03-1993
Publisher: Springer Science and Business Media LLC
Date: 25-11-2015
DOI: 10.1038/SREP17137
Abstract: Magnetic skyrmions have the potential to provide solutions for low-power, high-density data storage and processing. One of the major challenges in developing skyrmion-based devices is the skyrmions’ magnetic stability in confined helimagnetic nanostructures. Through a systematic study of equilibrium states, using a full three-dimensional micromagnetic model including demagnetisation effects, we demonstrate that skyrmionic textures are the lowest energy states in helimagnetic thin film nanostructures at zero external magnetic field and in absence of magnetocrystalline anisotropy. We also report the regions of metastability for non-ground state equilibrium configurations. We show that bistable skyrmionic textures undergo hysteretic behaviour between two energetically equivalent skyrmionic states with different core orientation, even in absence of both magnetocrystalline and demagnetisation-based shape anisotropies, suggesting the existence of Dzyaloshinskii-Moriya-based shape anisotropy. Finally, we show that the skyrmionic texture core reversal dynamics is facilitated by the Bloch point occurrence and propagation.
Publisher: AIP Publishing
Date: 30-03-2009
DOI: 10.1063/1.3105988
Abstract: The stray magnetic field of an array of hard ferromagnetic perpendicularly magnetized [Co/Pt]4 nanodots is used to nondestructively generate a periodic pinning potential for domain walls in an underlying [Pt/Co]2/Pt layer with perpendicular anisotropy. Pinning is evidenced using magneto-optical microscopy. The magnetic field (H) dependence of the average wall velocity in the presence of the periodic pinning potential is consistent with thermally activated creep, modified only by the addition of a uniform retarding field Hret, whose magnitude depends on the relative alignment of H and the dots' magnetizations.
Publisher: Springer Science and Business Media LLC
Date: 08-11-2019
Publisher: Elsevier BV
Date: 02-1991
Publisher: Elsevier BV
Date: 05-2004
Publisher: Elsevier BV
Date: 02-1992
Publisher: AIP Publishing
Date: 31-03-2008
DOI: 10.1063/1.2904697
Abstract: Collective spin wave modes propagating in an array of magnetic stripes coupled by dynamic dipole interaction are investigated by Brillouin light scattering. It is demonstrated that this structure supports propagation of discrete spin waves at any angle with respect to the stripes length. The data are interpreted using a theoretical model based on the Bloch wave approach. It is shown that, due to the one-dimensional artificial periodicity of the medium, the gaps in the spin wave spectrum are partial: the frequency passbands for propagation along the direction of periodicity overlap with the stop bands for propagation along the stripes.
Publisher: Wiley
Date: 30-04-2010
Publisher: Wiley
Date: 30-04-2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2004
Publisher: AIP Publishing
Date: 08-12-2022
DOI: 10.1063/5.0128526
Abstract: Excitations that may appear in cavity magnonics experiments are examined with numerical micromagnetics using a recently developed semi-classical cavity magnonics theory. The theory is generally applicable to linear and nonlinear dynamic systems. In this paper, ex le applications of the theory for magnetic systems are presented where the dynamics is described using numerical micromagnetics for field driven ferromagnets. Ex les of large litude driving are studied as a function of drive field litude and frequency. We comment also on large litude dynamics under elliptically polarized driving fields. The main conclusion is that when implemented together with micromagnetics, the theory can be used to describe cavity photon–magnon coupling for a wide variety of linear and nonlinear magnetic dynamics, thereby providing a useful technique for cavity magnonics.
Publisher: Elsevier BV
Date: 02-1991
Publisher: IOP Publishing
Date: 23-11-2016
Publisher: AIP Publishing
Date: 15-02-1991
DOI: 10.1063/1.348681
Abstract: Co/Pd multilayers with modulation wavelengths between 4 and 220 Å have been prepared by magnetically enhanced dc-triode sputtering on single-crystal sapphire substrates. Their saturation magnetization and volume and interface anisotropies have been investigated using Brillouin light scattering from collective spin waves and by SQUID magnetometry. The saturation magnetization of Co is found to be independent of the Co layer thickness and reduced by about 20% from the Co bulk value. From the comparison of the results of the two experimental methods, clear evidence for a Pd polarization is found and the polarization depth is estimated. S les with Co thicknesses of 2 atomic layers and Pd thicknesses ≥5 atomic layers exhibit a perpendicular magnetization due to a large negative out-of-plane interface anisotropy. The properties of spin waves in Co/Pd multilayers with the direction of magnetization pointing out-of-plane are discussed with respect to an appropriate theoretical model.
Publisher: IOP Publishing
Date: 10-09-2015
Publisher: American Physical Society (APS)
Date: 07-1989
Publisher: Elsevier BV
Date: 02-1992
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2008
Publisher: IOP Publishing
Date: 25-02-2009
DOI: 10.1088/0953-8984/21/12/124203
Abstract: Magnetic relaxation experiments have been used to investigate the non-equilibrium dynamics of FePt nanoparticles. The system exhibits ageing at low temperatures, as well as a narrow energy distribution of the barrier to reversal. These properties were found susceptible to being affected by particle size, matrix and applied field strength. An analysis based on broad rate distributions is presented and compared with results obtained using energy barrier and viscosity interpretations. We find that a single broad distribution of relaxation times suggestive of cooperative effects is sufficient to explain the experimental results.
Publisher: Elsevier BV
Date: 04-2002
Publisher: IOP Publishing
Date: 15-12-2011
DOI: 10.1088/0953-8984/24/2/024212
Abstract: We detail measurements of field-driven expansion and zero-field relaxation of magnetic mirror domains in antiferromagnetically coupled perpendicularly magnetized ultrathin Co layers. The zero-field stability of aligned ('mirror') domains in such systems results from non-homogeneous dipolar stray fields which exist in the vicinity of the domain walls. During field-driven domain expansion, we evidence a separation of the domain walls which form the mirror domain boundary. However, the walls realign, thereby reforming a mirror domain, if their final separation is below a critical distance at the end of the field pulse. This critical distance marks the point at which the effective net interaction between the walls changes from attractive to repulsive.
Publisher: American Physical Society (APS)
Date: 17-12-2015
Publisher: IOP Publishing
Date: 18-08-2021
Abstract: Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert d ing magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.
Publisher: Elsevier BV
Date: 2017
Publisher: IEEE
Date: 2002
Publisher: AIP Publishing
Date: 25-05-2004
DOI: 10.1063/1.1689771
Abstract: Zero-field magnetic viscosity measurements at low temperatures were made on a series of Pd40Ni40−xFexP20 (x=10–20) s les in order to determine the apparent magnetic-moment-weighted energy barrier distributions for these spin-glass alloys. The distributions observed are best described by a stretched exponential in the form of a truncated Lévy flight distribution. This form suggests a hierarchical landscape of apparent energy barriers arising from interactions between randomly oriented magnetic clusters within the material. The degree of stretching of the exponential form of the energy barrier distributions is found to increase with decreasing iron concentration.
Publisher: American Physical Society (APS)
Date: 02-1991
Publisher: IOP Publishing
Date: 16-08-2013
DOI: 10.1088/0953-8984/25/36/363201
Abstract: Lithographic processing and film growth technologies are continuing to advance, so that it is now possible to create patterned ferroic materials consisting of arrays of sub-1 μm elements with high definition. Some of the most fascinating behaviour of these arrays can be realised by exploiting interactions between the in idual elements to create new functionality. The properties of these artificial ferroic systems differ strikingly from those of their constituent components, with novel emergent behaviour arising from the collective dynamics of the interacting elements, which are arranged in specific designs and can be activated by applying magnetic or electric fields. We first focus on artificial spin systems consisting of arrays of dipolar-coupled nanomagnets and, in particular, review the field of artificial spin ice, which demonstrates a wide range of fascinating phenomena arising from the frustration inherent in particular arrangements of nanomagnets, including emergent magnetic monopoles, domains of ordered macrospins, and novel avalanche behaviour. We outline how demagnetisation protocols have been employed as an effective thermal anneal in an attempt to reach the ground state, comment on phenomena that arise in thermally activated systems and discuss strategies for selectively generating specific configurations using applied magnetic fields. We then move on from slow field and temperature driven dynamics to high frequency phenomena, discussing spinwave excitations in the context of magnonic crystals constructed from arrays of patterned magnetic elements. At high frequencies, these arrays are studied in terms of potential applications including magnetic logic, linear and non-linear microwave optics, and fast, efficient switching, and we consider the possibility to create tunable magnonic crystals with artificial spin ice. Finally, we discuss how functional ferroic composites can be incorporated to realise magnetoelectric effects. Specifically, we discuss artificial multiferroics (or multiferroic composites), which hold promise for new applications that involve electric field control of magnetism, or electric and magnetic field responsive devices for high frequency integrated circuit design in microwave and terahertz signal processing. We close with comments on how enhanced functionality can be realised through engineering of nanostructures with interacting ferroic components, creating opportunities for novel spin electronic devices that, for ex le, make use of the transport of magnetic charges, thermally activated elements, and reprogrammable nanomagnet systems.
Publisher: Elsevier BV
Date: 09-2006
Publisher: American Physical Society (APS)
Date: 25-10-2006
Publisher: American Physical Society (APS)
Date: 17-07-2012
Publisher: AIP Publishing
Date: 05-2007
DOI: 10.1063/1.2713231
Abstract: Local effective fields created in Fe by MnPd through exchange anisotropy are studied using an inductive ferromagnetic resonance technique. The bilayers were prepared on single crystal MgO(001) using ion beam sputtering in high vacuum and have a highly orientated crystalline structure with a [001] orientation as determined by x-ray diffraction. Unidirectional and fourfold anisotropies are measured using a stripline resonance geometry. Experiments with the field applied along different crystalline directions indicate that the fourfold axes are well defined with magnitudes consistent with values expected for bulk Fe. Anomalies in the frequency studied as a function of applied field are interpreted as evidence for a distribution of unidirectional anisotropy field orientations and strengths.
Publisher: American Chemical Society (ACS)
Date: 12-08-2015
DOI: 10.1021/ACS.NANOLETT.5B01953
Abstract: Spatially resolved analysis of magnetic properties on the nanoscale remains challenging, yet strain and defects on this length-scale can profoundly affect a material's bulk performance. We present a detailed investigation of the magnetic properties of La0.67Sr0.33MnO3 thin films in both free-standing and nanowire form and assess the role of strain and local defects in modifying the films' magnetic properties. Lorentz transmission electron microscopy is used to measure the magnetocrystalline anisotropy and to map the Curie temperature and saturation magnetization with nanometric spatial resolution. Atomic-scale defects are identified as pinning sites for magnetic domain wall propagation. Measurement of domain wall widths and crystalline strain are used to identify a strong magnetoelastic contribution to the magnetic anisotropy. Together, these results provide unique insight into the relationship between the nanostructure and magnetic functionality of a ferromagnetic complex oxide film.
Publisher: American Physical Society (APS)
Date: 16-11-2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2002
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4791226
Publisher: American Physical Society (APS)
Date: 21-12-1992
Publisher: AIP Publishing
Date: 11-02-2013
DOI: 10.1063/1.4792314
Abstract: Using Lorentz transmission electron microscopy, a unique experiment is realised in which an extended magnetic domain wall in a ferromagnetic nanowire, strongly pinned at one end, is utilised as a local probe of the distribution of pinning sites along the nanowire edges. Fresnel imaging is used to examine the detailed de-pinning process and extract a distribution of pinning energies along the wire. The pinning sites were found to be randomly distributed with surprisingly little correlation between pinning site location and visible structural features along the wire edge.
Publisher: American Physical Society (APS)
Date: 02-1991
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1999
DOI: 10.1109/20.801063
Publisher: Springer Science and Business Media LLC
Date: 02-2002
Publisher: Elsevier BV
Date: 07-2015
Publisher: American Physical Society (APS)
Date: 18-04-2016
Publisher: Springer Science and Business Media LLC
Date: 03-08-2014
DOI: 10.1038/NPHYS3072
Publisher: American Physical Society (APS)
Date: 13-10-2009
Publisher: Elsevier BV
Date: 1997
Publisher: AIP Publishing
Date: 2011
DOI: 10.1063/1.3526307
Abstract: Tangentially magnetized trigonal arrays of submicron Permalloy disks are characterized with ferromagnetic resonance to determine the possible contributions to frequency and linewidth from array disorder. Each array is fabricated by a water-surface self-assembly lithographic technique, and consists of a large trigonal array of 700 nm diameter magnetic disks. Each array is characterized by a different degree of ordering. Two modes are present in the ferromagnetic resonance spectra: a large litude, “fundamental” mode and a lower litude mode at higher field. Angular dependence of the resonance field in a very well ordered array is found to be negligible for both modes. The relationship between resonance frequency and applied magnetic field is found to be uncorrelated with array disorder. Linewidth is found to increase with increasing array disorder.
Publisher: Wiley
Date: 29-07-2010
Publisher: IOP Publishing
Date: 10-11-2000
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-1998
DOI: 10.1109/20.706300
Publisher: American Physical Society (APS)
Date: 09-2000
Publisher: American Physical Society (APS)
Date: 26-11-2007
Publisher: AIP Publishing
Date: 15-11-2010
DOI: 10.1063/1.3493242
Abstract: The broadband microstrip ferromagnetic resonance (FMR), cavity FMR, and Brillouin light scattering spectroscopy techniques have been applied for detection and characterization of a magnetic inhomogeneity in a film s le. In the case of a 100 nm thick permalloy film, an additional magnetically depleted top sublayer has been detected due to pinning effect it produces on the magnetization in the bulk of the film. The pinning results in appearance of an exchange standing spin wave mode in the broadband FMR absorption spectrum, whose litudes are different depending on whether the film or the film substrate faces the microstrip transducer. Comparison of the experimental litudes for this mode with results of our theory for both film placements revealed that the depleted layer is located at the film surface facing away from the film substrate. Subsequent broadband FMR characterization of a large number of other presumably single-layer films with thicknesses in the range 30–100 nm showed the same result.
Publisher: AIP Publishing
Date: 03-10-2022
DOI: 10.1063/5.0118078
Abstract: Geometrical designs of interacting nanomagnets have been studied extensively in the form of two-dimensional arrays called artificial spin ice. These systems are usually designed to create geometrical frustration and are of interest for the unusual and often surprising phenomena that can emerge. Advanced lithographic and element growth techniques have enabled the realization of complex designs that can involve elements arranged in three dimensions. Using numerical simulations employing the dumbbell approximation, we examine possible magnetic behaviors for bilayer artificial spin ice, in which the in idual layers are rotated with respect to one another. The goal is to understand how magnetization dynamics are affected by long-range dipolar coupling that can be modified by varying the layer separation and layer alignment through rotation. We consider bilayers where the layers are both either square or pinwheel arrangements of islands. Magnetic reversal processes are studied and discussed in terms of domain and domain wall configurations of the magnetic islands. Unusual magnetic ordering is predicted for special angles that define lateral spin superlattices for the bilayer systems.
Publisher: AIP Publishing
Date: 09-05-2003
DOI: 10.1063/1.1555311
Abstract: Spin-dependent tunneling through magnetic junctions is sensitive to material properties near the interface and in the barrier. Results of calculations are presented showing how electron transmission through a point contact tunnel junction is affected by atomic disorder in the barrier. Giant variations in the transmission probability are found with limited disorder. Sharp peaks appear in the tunnel current when defects exist at positions in the barrier that facilitate electron hopping across the contact. Consequences for thin film tunnel junction devices are also discussed, with reference to experiments showing strong spatial variations in tunnel current.
Publisher: American Physical Society (APS)
Date: 03-1993
Publisher: American Physical Society (APS)
Date: 10-2000
Publisher: American Physical Society (APS)
Date: 12-1991
Publisher: American Physical Society (APS)
Date: 25-09-2012
Publisher: IEEE
Date: 05-2006
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2001
DOI: 10.1109/20.951065
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1999
DOI: 10.1109/20.800666
Publisher: AIP Publishing
Date: 19-04-2007
DOI: 10.1063/1.2710068
Abstract: The geometry and method of spin wave excitation in planar waveguide inductive resonance methods is very different from that used in resonant cavity experiments, and correct interpretation of results requires an analysis which takes into account a number of features associated with the use of broadband microwave experiments. We consider aspects of a theoretical description of the resonance modes in ferromagnetic multilayers measured by a broadband inductive technique in a coplanar waveguide geometry. The effects of finite conductivity of the magnetic s le and contributions to the measured response from finite wavelength spin waves excited in this geometry are discussed. We also include the screening action of the coplanar line on the spin wave dispersion in the theory. We show that for a proper description of intensities, the theoretical model for the spin wave excitation has to include not only the contribution to intensities from the microwave current in the central conductor as did previous theories but also contributions from reverse currents in the ground half-planes of the coplanar waveguide.
Publisher: American Physical Society (APS)
Date: 06-04-2004
Publisher: American Physical Society (APS)
Date: 05-03-2010
Publisher: American Physical Society (APS)
Date: 11-2010
Publisher: IOP Publishing
Date: 18-09-2012
DOI: 10.1088/0953-8984/24/40/406003
Abstract: We present a theoretical discussion of surface polaritons on a ferroelectric-antiferromagnet with magnetoelectric coupling which allows the magnetic subsystem to be canted. Canting of the antiferromagnet results in weak ferromagnetism. The surface polaritons for a semi-infinite film are calculated for a propagation parallel to the uniaxial easy axis, leading to mixed modes. A superposition of two plane waves is needed to generate mixed surface modes. We find two branches, one near the magnon resonance frequency and the other near the phonon resonance frequency. We also find that the surface modes are non-reciprocal due to magnetoelectric interaction, such that ω(k) ≠ ω(-k), where ω is the frequency and k is the propagation vector.
Publisher: AIP Publishing
Date: 10-03-2017
DOI: 10.1063/1.4978315
Abstract: We present a comparative study of the spin wave properties in two magnetic films patterned into an artificial square spin ice-like geometry. The array elements are rectangular islands with the same lateral dimensions but with different thicknesses: 10 nm and 30 nm. Using Brillouin light scattering, the frequencies of spin wave excitations were measured as a function of the magnetic field going from positive to negative saturation. We find substantial changes with thickness to spin wave mode frequencies and the number of detected modes. Frequencies of spin waves localized at element edges are observed to evolve non-monotonically with magnetic fields and soften at critical fields. These critical fields enable us to extract information of the magnetization reversal of in idual islands within the array. Finally, we discuss the effects of separation between islands and examine the possibilities for dynamic coupling through the overlap of collective edge modes.
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2014
End Date: 2017
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2015
End Date: 2020
Funder: Engineering and Physical Sciences Research Council
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End Date: 2016
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2019
End Date: 2021
Funder: Canada Foundation for Innovation
View Funded ActivityStart Date: 2016
End Date: 2017
Funder: Engineering and Physical Sciences Research Council
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End Date: 2010
Funder: Australian Research Council
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