ORCID Profile
0000-0001-5313-4975
Current Organisation
University of Wollongong
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Publisher: Elsevier BV
Date: 05-2003
Publisher: IOP Publishing
Date: 06-2006
Publisher: AIP Publishing
Date: 15-02-2006
DOI: 10.1063/1.2171772
Abstract: An alternative method for determining the lock-in angle φL for pinning of the vortices on extended defects has been developed. This method does not require any preassumed criterion for defining φL. Highly twinned Sm1+xBa2−xCu3O6+y single crystal was used for demonstrating the method. Appropriate scaling of the hysteresis loops measured for different angles between the field and twin planes in highly twinned SmBaCuO single crystal led to a clear discrimination between two vortex dynamics regimes. From this scaling, the lock-in angle was determined to be 6°±0.1° for the single crystal investigated. This method significantly reduces the uncertainty in determining the lock-in angle when compared to all the other currently employed methods.
Publisher: AIP Publishing
Date: 29-04-2004
DOI: 10.1063/1.1741036
Abstract: On the basis of exact solutions to the London equation, the magnetic moment of a type II superconductor filament surrounded by a soft-magnet environment is calculated and the procedure of extracting the superconductor contribution from magnetic measurements is suggested. A comparison of theoretical results with experiments on MgB2/Fe wires allows the estimation of the value of critical current for the first magnetic flux penetration.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-1997
DOI: 10.1109/77.620773
Publisher: AIP Publishing
Date: 25-04-2007
DOI: 10.1063/1.2710451
Abstract: We report the influence of the sintering temperature on the electromagnetic behavior for the RuSr2Eu1.5Ce0.5Cu2O10 material, in which superconductivity and ferromagnetism coexist. The inadequate heat treatment results in the coexistence of the secondary Ru-1212 phase along with the dominant Ru-1222 phase. The presence of two phases leads to the magnetic superposition of the signals from both phases, which results in the observation of a small peak around 120–130K. In the pure Ru-1222 no such magnetic anomaly is observed. In addition, the impure s les exhibit a double step superconductivity transition. In the normal state, these impure s les exhibit a semiconductinglike behavior of the resistivity. In contrast, the pure Ru-1222 s le with much larger, well connected grains has a single step resistivity transition, as well as a metalliclike behavior in the normal state. Our work sends a strong message that only high quality, phase pure s les can be chosen for the investigation of the complex behavior in the Ru system.
Publisher: IOP Publishing
Date: 27-11-2008
Publisher: Springer Science and Business Media LLC
Date: 10-2000
Publisher: Elsevier BV
Date: 03-2004
Publisher: Elsevier BV
Date: 12-2010
Publisher: Elsevier BV
Date: 2004
Publisher: IOP Publishing
Date: 26-09-2002
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2007
Publisher: Elsevier BV
Date: 09-2007
Publisher: World Scientific Pub Co Pte Lt
Date: 10-07-2009
DOI: 10.1142/S0217979209062918
Abstract: The quality superconducting YBa 2 Cu 3 O 7 films and YBa 2 Cu 3 O 7 / NdBa 2 Cu 3 O 7 multilayered film structures have been grown by pulsed laser deposition on metallic templates with magnesium oxide (MgO) buffer layer grown by incline substrate deposition. Different supplementary buffer layers have been deposited between the superconductor and MgO buffer layer. This additional buffer layer reduces the crystal structure misalignment of the superconducting layers. The critical current density has been observed to be higher in the multilayered structures in comparison with the same thickness of monolayer YBa 2 Cu 3 O 7 films. The origin of this enhancement is the improved microstructure of the multilayered systems obtained.
Publisher: AIP Publishing
Date: 09-2001
DOI: 10.1063/1.1401182
Abstract: The behavior of the ensemble of vortices in the Shubnikov phase in biaxially oriented films of the high-temperature superconductor YBa2Cu3O7−δ (YBCO) in an applied magnetic field is investigated for different orientations of the field. The techniques used are the recording of the current–voltage characteristics in the transport current and of resonance curves and d ing of a mechanical oscillator during the passage of a transport current. It is shown that the behavior of the vortex ensemble in YBCO films, unlike the case of single crystals, is determined by the interaction of the vortices with linear defects—edge dislocations, which are formed during the pseudomorphic epitaxial growth and are the dominant type of defect of the crystal lattice, with a density reaching 1015 lines/m2. The effective pinning of the vortices and the high critical current density (Jc⩾3×1010 A/m2 at 77 K) in YBCO films are due precisely to the high density of linear defects. New phase states of the vortex matter in YBCO films are found and are investigated in quasistatics and dynamics they are due to the interaction of the vortices with crystal defects, to the onset of various types of disordering of the vortex lattice, and to the complex depinning process. A proposed H–T phase diagram of the vortex matter for YBCO films is proposed.
Publisher: AIP Publishing
Date: 05-2010
DOI: 10.1063/1.3366610
Abstract: The universal approach of liquid mixing has been found to produce “organic” MgB2−xCx superconductors with structural and supercurrent-carrying properties unattainable by other techniques. We show by transmission electron microscopy combined with energy dispersive spectroscopy that these unique properties are enabled through coating of boron particles with a nanolayer of carbon. The subsequent reaction between carbon-encapsulated boron and magnesium results in enhanced carbon content x in the crystal lattice, as determined by x-ray diffraction pattern analysis. Among various carbon-containing compounds investigated, polycarbosilane has been found to be the optimal dopant for MgB2 superconductor, producing the largest critical current density due to the formation of wide range of nanodefects with pinning properties within the MgB2 crystal lattice, as well as due to minimal formation of current-blocking layers around the grains.
Publisher: American Physical Society (APS)
Date: 29-11-2006
Publisher: AIP Publishing
Date: 30-06-2004
DOI: 10.1063/1.1763224
Abstract: Magnetic measurements carried out on MgB2 superconducting round wires have shown that the critical current density Jc(Ba) in wires sheathed by iron can be significantly higher than that in the same bare (unsheathed) wires over a wide applied magnetic field Ba range. The magnetic behavior is, however, strongly dependent on the magnetic history of the sheathed wires, as well as on the wire orientation with respect to the direction of the applied field. The behavior observed can be explained by magnetic interaction between the soft magnetic sheath and superconducting core, which can result in a redistribution of supercurrents in the flux filled superconductor. A phenomenological model explaining the observed behavior is proposed.
Publisher: Elsevier BV
Date: 03-2000
Publisher: IOP Publishing
Date: 10-01-2002
Publisher: IOP Publishing
Date: 02-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
Publisher: Elsevier BV
Date: 09-2002
Publisher: Wiley
Date: 21-05-2007
Publisher: Elsevier BV
Date: 05-2003
Publisher: American Physical Society (APS)
Date: 16-02-2006
Publisher: AIP Publishing
Date: 18-07-2003
DOI: 10.1063/1.1586467
Abstract: We investigated the effect of SiC nanoparticle doping on the crystal lattice structure, critical temperature Tc, critical current density Jc, and flux pinning in MgB2 superconductor. A series of MgB2−x(SiC)x/2 s les with x=0–1.0 were fabricated using an in situ reaction process. The contraction of the lattice and depression of Tc with increasing SiC doping level remained rather small most likely due to the counterbalancing effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intragrain defects and highly dispersed nanoinclusions within the grains which can act as effective pinning centers for vortices, improving Jc behavior as a function of the applied magnetic field. The enhanced pinning is mainly attributable to the substitution-induced defects and local structure fluctuations within grains. A pinning mechanism is proposed to account for different contributions of different defects in MgB2−x(SiC)x/2 superconductors.
Publisher: AIP Publishing
Date: 21-04-2010
DOI: 10.1063/1.3365616
Abstract: To describe the critical current density (Jc) as the function of applied magnetic field (Ba) in high quality YBa2Cu3O7 (YBCO) superconducting films, the vortex pinning mechanism along the structural domain boundaries of the films is developed. The boundaries, assumed to have low misorientation angles, are quantitatively considered to consist of in idual edge dislocations acting as pinning wells, rather than a continuous boundary. This extended model accurately describes the experimental Jc(Ba) over the wide field and temperature ranges. Marginal deviations of the model from the experimental Jc(Ba) curves are observed at high fields and temperatures where thermally activated depinning is significant. This pinning model is verified to provide precise structural properties of the films which can be obtained by other considerations.
Publisher: IOP Publishing
Date: 18-10-2002
Publisher: Elsevier BV
Date: 10-2010
Publisher: IOP Publishing
Date: 06-2020
DOI: 10.1088/1742-6596/1559/1/012048
Abstract: Comprehensive experimental results of fully oxidized (up to YBa 2 Cu 3 O 6,9-7 ) melt-textured YBaCuO materials with different microstructures are presented. These microstructures are built respectively: (1) with a high dislocations density but almost without twins (after high temperature treatment at 2 GPa) and (2) with a high twin density, but practically free from dislocations and stacking faults (after high temperature oxygenation at 10-16 MPa). It is shown that for attaining high critical current densities and fields of irreversibility ( j c( H ‖ c , 0 T)=9·10 4 A/cm 2 , H irr =9.7 T at 77 K), a high twin density in YBa 2 Cu 3 O 6.9-7 matrix of MT-YBCO is required. The density of twins in fully oxidized materials depends on the distances between Y 2 BaCuO 5 inclusions, larger twin densities are related to shorter distances between inclusions. The influence of phase composition of the initial powder mixtures on the distances between Y 2 BaCuO 5 inclusions have been characterized and discussed.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2005
Publisher: IOP Publishing
Date: 06-2006
Publisher: Elsevier BV
Date: 11-2009
Publisher: AIP Publishing
Date: 05-2010
DOI: 10.1063/1.3365576
Abstract: Temperature and magnetic field dependent neutron diffraction has been used to study the magnetic order in Ru0.9Sr2YCu2.1O7.9. The appearance of (1/2, 1/2, 1/2), (1/2, 1/2, 3/2), and (1/2, 1/2, 5/2) peaks below TM=140 K manifests the antiferromagnetic order. Neutron diffraction patterns measured in applied magnetic fields from 0 to 6 T show the destruction of the antiferromagnetic order with increasing field. There is no evidence of spontaneous or field-induced long range ferromagnetic order. This latter result contradicts the vast majority of other experimental observations for this system.
Publisher: IOP Publishing
Date: 04-02-2020
Publisher: Springer Science and Business Media LLC
Date: 06-2013
Publisher: IOP Publishing
Date: 07-11-2003
Publisher: Elsevier BV
Date: 04-2002
Publisher: Trans Tech Publications, Ltd.
Date: 04-2003
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2017
Publisher: AIP Publishing
Date: 04-10-2004
DOI: 10.1063/1.1790069
Abstract: High-quality bulk MgB2 exhibits a structure of voids and agglomeration of crystals on different length scales. Because of this, the superconducting currents percolate between the voids in the ensuing structure. Magnetic measurements reveal that the superconducting currents circulate on at least three different length scales, of ∼1μm, ∼10μm, and whole of the s le (∼millimeter). Each of these screenings contributes to the measured irreversible magnetic moment (Δm). The analysis of the field dependence of Δm for s les of subsequently decreasing size showed that the critical current obtained using the simple critical state model is erroneous. This leads to the artifact of the s le size-dependent critical current density Jc and irreversibility field. Our data analysis enables the separation of the contribution of each of the screening currents to Δm. The field dependence of each of the currents follows a stretched exponential form. The currents flowing around whole of the s le give a dominant contribution to Δm in the intermediate fields (1T& H& T at 20K) and they can be used to obtain the value of Jc from critical state model, which corresponds to the transport Jc. The stretched exponential field dependence of these currents is similar to the one obtained for high-temperature superconductors, and it seems to be connected with the percolation of the currents.
Publisher: AIP Publishing
Date: 05-06-2006
DOI: 10.1063/1.2211051
Abstract: Much smoother surfaces and significantly improved superconducting properties of relatively thick YBa2Cu3O7 (YBCO) films have been achieved by introducing a multilayered structure with alternating main YBCO and additional NdBCO layers. The surface of thick (1μm) multilayers has almost no holes compared to YBCO films. Critical current density (Jc) has been drastically increased up to a factor & in 1μm multilayered structures compared to YBCO films over entire temperature and applied magnetic field range. Moreover, Jc values measured in thick multilayers are even larger than in much thinner YBCO films. The Jc and surface improvement have been analyzed and attributed to growth conditions and corresponding structural peculiarities.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2007
Publisher: AIP Publishing
Date: 10-2019
DOI: 10.1063/1.5112804
Abstract: High quality robust two-dimensional electron gas (2DEG) LaAlO3/SrTiO3 (LAO/STO) interfaces are produced using pulsed laser deposition and an acid-free substrate Ti-termination process, resulting in single unit cell terraces. Temperature dependent resistance measurements show two hysteresis anomalies around 80 K and 160 K. By using Hall measurements, we find an Arrhenius dependence in charge carrier density describing a partial carrier freeze-out below ∼80 K. We show that these two resistance anomalies are unrelated to the temperature dependence of the charge carrier density despite the tempting coincidence of the low temperature hysteresis feature and the freeze-out process. A two-carrier model is required to accurately estimate the activation energy of the thermally activated type charge carriers, which are found to be ∼5 to 7 meV. These results support the theory that oxygen vacancy defects contribute to the metallic conductivity at the 2DEG LAO/STO interface even for annealed s les.
Publisher: American Physical Society (APS)
Date: 15-11-2004
Publisher: IOP Publishing
Date: 15-04-2004
Publisher: IOP Publishing
Date: 06-2010
Publisher: AIP Publishing
Date: 02-10-2006
DOI: 10.1063/1.2358947
Abstract: The effect of carbohydrate doping on lattice parameters, microstructure, Tc, Jc, Hirr, and Hc2 of MgB2 has been studied. In this work the authors used malic acid as an ex le of carbohydrates as an additive to MgB2. The advantages of carbohydrate doping include homogeneous mixing of precursor powders, avoidance of expansive nanoadditives, production of highly reactive C, and significant enhancement in Jc, Hirr, and Hc2 of MgB2, compared to undoped s les. The Jc for MgB2+30wt% C4H6O5 s le was increased by a factor of 21 at 5K and 8T without degradation of self-field Jc.
Publisher: Elsevier BV
Date: 12-2007
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2019
Publisher: Elsevier BV
Date: 11-2002
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2011
Publisher: Elsevier BV
Date: 09-2007
Publisher: Elsevier BV
Date: 09-2007
Publisher: American Physical Society (APS)
Date: 08-1999
Publisher: Royal Society of Chemistry (RSC)
Date: 2002
DOI: 10.1039/B111186H
Publisher: IOP Publishing
Date: 06-2006
Publisher: AIP Publishing
Date: 20-12-2018
DOI: 10.1063/1.5063261
Abstract: The critical current density, Jc, can be increased by introducing defects throughout YBa2Cu3O7 superconducting thin films. We propose a new approach of substrate nanoengineering to produce well-controlled defects. LaAlO3 substrates have been ion-etched with different 34 nm deep patterns prior to the deposition of the films. An annealing step at 1000 °C after substrate etching has been undertaken to negate the Ar-ion damage to the surface. The Jc of the so-prepared s les measured at different temperatures has been compared to thin films deposited on plain substrates at the same time. In general, an increase in Jc is observed across all temperatures and fields as a result of both patterning and annealing. In particular, at zero field and 85 K, the largest enhancement of & % has been recorded for circle and triangle patterns. This new substrate nanoengineering technique is very promising for flux trapping of superconducting devices, particularly because an increase to critical current (Ic) also occurs. Further optimization of depth, size, and shape of the patterns is expected to produce further improvements to Jc.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NR01210E
Abstract: A giant ferromagnetic/superconducting proximity effect is demonstrated to be controllable by an external magnetic field.
Publisher: American Physical Society (APS)
Date: 13-01-2004
Publisher: IOP Publishing
Date: 02-2008
Publisher: AIP Publishing
Date: 06-02-2009
DOI: 10.1063/1.3063069
Abstract: Systematic dc and ac magnetic susceptibility measurements performed on RuSr2Eu1.5Ce0.5Cu2O10−δ (Ru1222) demonstrate a paramagnetic to ferromagnetic transition around 95 K. The third harmonic of the ac susceptibility reveals that the system undergoes a spin glass transition below 75 K. The features of the zero-field cooled and field cooled dc magnetization curves of Ru1222 material resemble those of a cluster glass state, rather than those of a canonical spin glass state. The magnetization versus applied field loops do not saturate, even at very high applied fields, resulting in the short range magnetic order in the system, which facilitates the formation of clusters that freeze at low temperature. The temperature dependence of the second and third harmonic ac susceptibilities further confirms the coexistence of a cluster glass state and ferromagnetic order in the Ru1222 system.
Publisher: Springer Science and Business Media LLC
Date: 26-09-2021
Publisher: Springer Science and Business Media LLC
Date: 24-03-2010
Publisher: Elsevier BV
Date: 09-2007
Publisher: American Physical Society (APS)
Date: 04-02-2013
Publisher: Elsevier BV
Date: 05-2003
Publisher: Springer Science and Business Media LLC
Date: 29-06-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2003
Publisher: Elsevier BV
Date: 11-2020
Publisher: IOP Publishing
Date: 20-11-2007
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2007
Publisher: World Scientific Pub Co Pte Lt
Date: 10-07-0017
DOI: 10.1142/S0217979209062840
Abstract: Systematic investigation of structural, magnetic and transport properties of RuSr 2 RE 2-x Ce x Cu 2 O 10 with RE being Sm and Eu has been performed. We present the experimental evidence that the synthesis of RuSr 2 Eu 1.5 Ce 0.5 Cu 2 O 10 under non-optimised heat treatment conditions may results in the formation of secondary RuSr 2 EuCu 2 O 8 phase. In contrast, similar preparation conditions for RuSr 2 Sm 1.5 Ce 0.5 Cu 2 O 10 s les lead to the pure phase. Consequently, RuSr 2 Eu 1.5 Ce 0.5 Cu 2 O 10 s les exhibit a small peak around 125 K in the temperature dependence of dc magnetization, pronounced irreversibility between zero-field cooled and field cooled curves at temperatures higher than the peak temperature, and the bell shaped behavior of the coercive field as the function of temperature above Curie's temperature. These anomalous features, which may arise due to the superposition effect of the main and secondary phases, which are both magnetic, are completely absent for RuSr 2 Sm 1.5 Ce 0.5 Cu 2 O 10 s le, which does not consist of the secondary phase.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
Publisher: American Physical Society (APS)
Date: 11-04-2008
Publisher: AIP Publishing
Date: 13-11-2006
DOI: 10.1063/1.2388126
Abstract: A magnetic field of up to 12T was applied during the sintering process of pure MgB2 and carbon nanotube (CNT) doped MgB2 wires. The authors have demonstrated that magnetic field processing results in grain refinement, homogeneity, and enhancement in Jc(H) and Hirr. The extent of improvement in Jc increases with increasing field. The Jc for a 10T field processed CNT doped s le increases by a factor of 3 at 10K and 8T and at 20K and 5T, respectively. Hirr for the 10T field processed CNT doped s le reached 9T at 20K, which exceeded the best value of SiC doped MgB2 at 20K. Magnetic field processing reduces the resistivity in CNT doped MgB2, straightens the entangled CNTs, and improves the adherence between CNTs and the MgB2 matrix.
Publisher: Elsevier BV
Date: 09-2005
Publisher: American Chemical Society (ACS)
Date: 15-05-2020
Publisher: Elsevier BV
Date: 05-2013
Publisher: IOP Publishing
Date: 17-03-2009
Publisher: IOP Publishing
Date: 10-08-2004
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2007
Publisher: IOP Publishing
Date: 13-10-2011
DOI: 10.1088/0953-8984/23/43/435702
Abstract: In this work, we present magnetic phase diagrams of a RuSr(2)Eu(1.5)Ce(0.5)Cu(2)O(10-δ) (Ru-1222) superconducting ferromagnet derived from its static and dynamic magnetic responses, measured by temperature and field dependences of dc magnetization and nonlinear ac susceptibility in both low and high magnetic fields. Comparison of magnetic phase diagrams of phase pure and impure s les singles out the intrinsic and extrinsic magnetic features, naturally proposing a unified model of Ru-1222 magnetic behaviour. The results considered within the proposed interpretation indicate full agreement between static and dynamic properties which, if measured in combination, effectively complement each other, uncovering existing ambiguities.
Publisher: Elsevier BV
Date: 12-2010
Publisher: Wiley
Date: 09-1999
DOI: 10.1002/(SICI)1521-3951(199909)215:1<573::AID-PSSB573>3.0.CO;2-8
Publisher: Elsevier BV
Date: 08-2004
Publisher: IOP Publishing
Date: 09-09-2003
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2011
Publisher: IOP Publishing
Date: 07-09-2005
Publisher: American Physical Society (APS)
Date: 06-07-2006
Publisher: IOP Publishing
Date: 10-04-2003
Publisher: AIP Publishing
Date: 02-2010
DOI: 10.1063/1.3298507
Abstract: To avoid the occurrence of doped magnetic ion clustering is a challenge in fabrication of diluted magnetic semiconductors (DMSs). In this work, we report the intrinsic ferromagnetic behavior in Co-doped ZnO DMSs induced by Eu codoping. Both structural parameters and magnetic properties demonstrate the existence of an interaction between Co and Eu ions. The observation of multiplet structures for the localized Co 3d states in x-ray absorption and x-ray magnetic circular dichroism characterization evidences that the codoped Eu plays an important role in facilitating the Co substitution of Zn, leading to intrinsic ferromagnetism.
Publisher: Elsevier BV
Date: 11-2000
Publisher: Springer-Verlag
Date: 2005
Publisher: Elsevier BV
Date: 08-1995
Publisher: IOP Publishing
Date: 13-08-2013
Publisher: Trans Tech Publications, Ltd.
Date: 06-2010
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.654-656.1704
Abstract: High temperature superconducting YBa2Cu3O7 films have been prepared by pulsed laser deposition on top of single crystal substrates and metallic templates. Films have been investigated in order to determine the influence of microstructural peculiarities on the critical current density. It has been found that there is an inherent mechanism limiting the superconductive current flow in YBa2Cu3O7 film deposited on metallic template. This mechanism is associated with YBa2Cu3O7 film architecture, fabrication procedure and following low temperature usage.
Publisher: Elsevier BV
Date: 05-1998
Publisher: American Physical Society (APS)
Date: 27-02-2006
Publisher: IOP Publishing
Date: 27-08-2020
No related grants have been discovered for Alexey V Pan.