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Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6TA01994C
Abstract: Gd/Ag co-doping is an effective way to simultaneously reduce the lattice thermal conductivity and enhance the Seebeck coefficient of SnTe-based thermoelectric materials.
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 02-2017
Publisher: AIP Publishing
Date: 23-01-2015
DOI: 10.1063/1.4906437
Abstract: The structural properties of Mn0.92Fe0.08CoGe have been investigated in detail using synchrotron x-ray diffraction in zero and applied pressure (p = 0–10 GPa). A ferromagnetic transition occurs around TC = 300 K and a large magnetic-entropy change −ΔSM = 17.3 J/kg K detected at TC for a field change of ΔB = 5 T. The field dependence of −ΔSMmax can be expressed as −ΔSMmax ∝ B. At ambient temperature and pressure, Mn0.92Fe0.08CoGe exhibits a co-existence of the orthorhombic TiNiSi-type structure (space group Pnma) and hexagonal Ni2In-type structure (space group P63/mmc). Application of external pressure drives a structure change from the orthorhombic TiNiSi-type structure to the hexagonal Ni2In-type structure. A large anomaly in heat capacity around TC is detected and the Debye temperature θD (=319(±10) K) has been derived from analyses of the low temperature heat capacity, T ≲ 10 K.
Publisher: Springer Science and Business Media LLC
Date: 19-12-2016
DOI: 10.1038/NCOMMS13807
Abstract: The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric iezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.
Publisher: Elsevier BV
Date: 09-2023
Publisher: Springer Science and Business Media LLC
Date: 18-05-2023
Publisher: American Physical Society (APS)
Date: 05-05-2008
Publisher: Springer Science and Business Media LLC
Date: 20-11-2012
Publisher: American Chemical Society (ACS)
Date: 04-12-2014
DOI: 10.1021/JA510433J
Abstract: Surfactant-free CuAgSe nanoparticles were successfully synthesized on a large scale within a short reaction time via a simple environmentally friendly aqueous approach under room temperature. The nanopowders obtained were consolidated into pellets for investigation of their thermoelectric properties between 3 and 623 K. The pellets show strong metallic characteristics below 60 K and turn into an n-type semiconductor with increasing temperature, accompanied by changes in the crystal structure (i.e., from the pure tetragonal phase into a mixture of tetragonal and orthorhombic phases), the electrical conductivity, the Seebeck coefficient, and the thermal conductivity, which leads to a figure of merit (ZT) of 0.42 at 323 K. The pellets show further interesting temperature-dependent transition from n-type into p-type in electrical conductivity arising from phase transition (i.e., from the mixture phases into cubic phase), evidenced by the change of the Seebeck coefficient from -28 μV/K into 226 μV/K at 467 K. The ZT value increased with increasing temperature after the phase transition and reached 0.9 at 623 K. The sintered CuAgSe pellets also display excellent stability, and there is no obvious change observed after 5 cycles of consecutive measurements. Our results demonstrate the potential of CuAgSe to simultaneously serve (at different temperatures) as both an n-type and a p-type thermoelectric material.
Publisher: Springer Science and Business Media LLC
Date: 11-06-2014
DOI: 10.1038/SREP05255
Publisher: AIP Publishing
Date: 03-09-2012
DOI: 10.1063/1.4751990
Abstract: Exchange bias effects were studied in the simple perovskite NdMnO3. Nd3+ ordering is induced by the Mn3+ ferromagnetic component, and they are antiferromagnetically coupled with each other. At 30 K, both negative and positive exchange bias effects are found, which are dependent on the cooling field. The exchange bias fields are around −2400 Oe and 1800 Oe, respectively. Positive and negative exchange bias effects were also observed at 8 K, but the exchange bias fields are only 130 Oe and −120 Oe. The coupling intensity between Nd3+ ordering and Mn3+ ordering, and their initial states determine the polarity of the exchange bias fields.
Publisher: American Physical Society (APS)
Date: 23-05-2013
Publisher: MDPI AG
Date: 17-06-2021
Abstract: MnCoGe-based compounds have been increasingly studied due to their possible large magnetocaloric effect correlated to the magnetostructural coupling. In this research, a comprehensive study of structure, magnetic phase transition, magnetocaloric effect and thermomechanical properties for MnCoGe1−xSix is reported. Room temperature X-ray diffraction indicates that the MnCoGe1−xSix (x = 0, 0.05, 0.1, 0.15 and 0.2) alloys have a major phase consisting of an orthorhombic TiNiSi-type structure with increasing lattice parameter b and decreasing others (a and c) with increasing Si concentration. Along with M-T and DSC measurements, it is indicated that the Tc value increased with higher Si concentration and decreased for structural transition temperature Tstr. The temperature dependence of the magnetization curves overlaps completely, indicating that there is no thermal hysteresis, and it is shown that the transition is the second-order type. It is also shown that the decreased magnetization on the replacement of Si for Ge decreases the value of −ΔSM from −ΔSM~8.36 J kg−1 K−1 at x = 0 to −ΔSM~5.49 J kg−1 K−1 at x = 0.2 with 5 T applied field. The performed Landau theory has confirmed the second-order transition in this study, which is consistent with the Banerjee criterion. The magnetic measurement and thermomechanical properties revealed the structural transition that takes place with Si substitution of Ge.
Publisher: Springer Science and Business Media LLC
Date: 16-10-2011
Publisher: Springer Science and Business Media LLC
Date: 05-11-2021
DOI: 10.1038/S41427-021-00338-4
Abstract: Materials exhibiting zero thermal expansion (ZTE), namely, volume invariance with temperature change, can resist thermal shock and are highly desired in modern industries for high-precision components. However, pure ZTE materials are rare, especially those that are metallic. Here, we report the discovery of a pure metallic ZTE material: an orthorhombic Mn 1- x Ni x CoSi spiral magnet. The introduction of Ni can efficiently enhance the ferromagnetic exchange interaction and construct the transition from a spiral magnetic state to a ferromagnetic-like state in MnCoSi-based alloys. Systematic in situ neutron powder diffraction revealed a new cycloidal spiral magnetic structure in the bc plane in the ground state, which transformed to a helical spiral in the ab plane with increasing temperature. Combined with Lorentz transmission electron microscopy techniques, the cycloidal and helical spin order coherently rotated at varying periods along the c -axis during the magnetic transition. This spin rotation drove the continuous movement of the coupled crystalline lattice and induced a large negative thermal expansion along the a -axis, eventually leading to a wide-temperature ZTE effect. Our work not only introduces a new ZTE alloy but also presents a new mechanism by which to discover or design ZTE magnets.
Publisher: Research Square Platform LLC
Date: 05-04-2021
DOI: 10.21203/RS.3.RS-361418/V1
Abstract: To reach a closed-loop material system and meet the urgent requirement of sustainable energy storage technologies, it is essential to incorporate efficient waste management into designing new energy storage materials. Here, we reported a “two birds with one stone” strategy to transform rusty iron products into Prussian blue as high-performance cathode materials and recover the rusty iron products to their original status. Owing to the high crystalline and Na + content, the rusty iron derived Prussian blue shows a high specific capacity of 145 mAh g − 1 and excellent cycling stability over 3500 cycles. Through the in situ X-ray diffraction and in situ Raman spectra, it is found that the impressive ion storage capability and stability are greatly related to the suppressed structure distortion during the charge/discharge process. The ions migration mechanism and possibility as universal host of other kinds of ions are further illuminated by density functional theory calculations. This work provides a new strategy for recycling wasted materials into high value-added materials for sustainable battery systems, and is adaptable in the nanomedicine, catalysis, sensors, and gas storage applications.
Publisher: American Chemical Society (ACS)
Date: 13-09-2023
Publisher: AIP Publishing
Date: 27-01-2014
DOI: 10.1063/1.4863230
Abstract: A giant magnetocaloric effect has been observed around the Curie temperature, TC ∼ 42 K, in NdMn1.7Cr0.3Si2 with no discernible thermal and magnetic hysteresis losses. Below 400 K, three magnetic phase transitions take place around 380 K, 320 K and 42 K. Detailed high resolution synchrotron and neutron powder diffraction (10–400 K) confirmed the magnetic transitions and phases as follows: TNintra ∼ 380 K denotes the transition from paramagnetism to intralayer antiferromagnetism (AFl), TNinter ∼ 320 K represents the transition from the AFl structure to the canted antiferromagnetic spin structure (AFmc), while TC ∼ 42 K denotes the first order magnetic transition from AFmc to canted ferromagnetism (Fmc + F(Nd)) due to ordering of the Mn and Nd sub-lattices. The maximum values of the magnetic entropy change and the adiabatic temperature change, around TC for a field change of 5 T are evaluated to be −ΔSMmax ∼ 15.9 J kg−1 K−1 and ΔTadmax ∼ 5 K, respectively. The first order magnetic transition associated with the low levels of hysteresis losses (thermal & ∼0.8 K magnetic field & ∼0.1 T) in NdMn1.7Cr0.3Si2 offers potential as a candidate for magnetic refrigerator applications in the temperature region below 45 K.
Publisher: American Chemical Society (ACS)
Date: 12-03-2015
DOI: 10.1021/CM504091Z
Publisher: Springer Science and Business Media LLC
Date: 19-03-2018
DOI: 10.1038/S41563-018-0034-4
Abstract: Piezoelectric materials, which respond mechanically to applied electric field and vice versa, are essential for electromechanical transducers. Previous theoretical analyses have shown that high piezoelectricity in perovskite oxides is associated with a flat thermodynamic energy landscape connecting two or more ferroelectric phases. Here, guided by phenomenological theories and phase-field simulations, we propose an alternative design strategy to commonly used morphotropic phase boundaries to further flatten the energy landscape, by judiciously introducing local structural heterogeneity to manipulate interfacial energies (that is, extra interaction energies, such as electrostatic and elastic energies associated with the interfaces). To validate this, we synthesize rare-earth-doped Pb(Mg
Publisher: AIP Publishing
Date: 15-04-2008
DOI: 10.1063/1.2909203
Abstract: MgB 2 / Fe wires with 10 at. % excess Mg produced by in situ powder-in-tube processing were compared to normal stoichiometric MgB2/Fe wires prepared by the same method. It was found that the critical current density (Jc) and the irreversibility field (Hirr) were significantly enhanced for MgB2/Fe wires with excess Mg. The transport Jc for 10 at. % Mg excess s les sintered at 800 °C, measured at a field of up to 14 T, increased by a factor of 2 compared to that for the normal MgB2 wires. The best Jc results for the 10 at. % Mg excess s le were obtained by heating the s le at 600 °C for 1 h the Jc at a field of 8 T and at temperature of 10 K reached 3×104 A/cm2. The detailed analysis of the effect of excess Mg on the microstructures, the Jc, and the Hirr, of MgB2/Fe wires are presented in this paper.
Publisher: American Chemical Society (ACS)
Date: 16-12-2021
Abstract: Environmentally friendly lead-free piezoelectric materials have been attracting significant attention in recent years. Na
Publisher: American Physical Society (APS)
Date: 04-03-2013
Publisher: AIP Publishing
Date: 04-2011
DOI: 10.1063/1.3562518
Abstract: Polycrystalline (PC) and single crystalline (SC) Ca-doped LaCoO3 (LCCO) s les with the perovskite structure were synthesized by conventional solid-state reaction and the floating-zone growth method. We present the results of a comprehensive investigation of the magnetic properties of the LCCO system. Systematic measurements have been conducted on dc magnetization, ac susceptibility, exchange-bias, and the magnetocaloric effect. These findings suggest that complex structural phases, ferromagnetic (FM), and spin-glass/cluster-spin-glass (CSG), and their transitions exist in PC s les, while there is a much simpler magnetic phase in SC s les. It was also of interest to discover that the CSG induced a magnetic field memory effect and an exchange-bias-like effect, and that a large inverse irreversible magnetocaloric effect exists in this system.
Publisher: Springer Science and Business Media LLC
Date: 02-12-2014
Publisher: AIP Publishing
Date: 06-06-2011
DOI: 10.1063/1.3599456
Abstract: A giant magnetocaloric effect has been observed in NdMn2Ge0.4Si1.6 associated with the first-order magnetic phase transition from antiferromagnetism to ferromagnetism around TC=36K. The magnetic entropy change –ΔSM and adiabatic temperature change ΔTad have been determined from magnetization and specific heat measurements (B=0–5 T) with –ΔSM calculated by the Maxwell relation and Clausius–Clapeyron method. The values –ΔSMmax=12.3 J kg−1 K−1 and refrigerant capacity ∼95 J/kg for ΔB=0–2 T as derived from the Maxwell relation, together with the small hysteresis (thermal & .5 K magnetic field & .1 T), indicate the potential of NdMn2Ge0.4Si1.6 for refrigeration applications.
Publisher: Elsevier BV
Date: 04-2015
Publisher: AIP Publishing
Date: 04-05-2015
DOI: 10.1063/1.4919895
Abstract: Structural and magnetic properties in TbMn2Si2 are studied by variable temperature X-ray diffraction, magnetization, electrical resistivity, and heat capacity measurements. TbMn2Si2 undergoes two successive magnetic transitions at around Tc1 = 50 K and Tc2 = 64 K. Tc1 remains almost constant with increasing magnetic field, but Tc2 shifts significantly to higher temperature. Thus, there are two partially overlapping peaks in the temperature dependence of magnetic entropy change, i.e., −ΔSM (T). The different responses of Tc1 and Tc2 to external magnetic field, and the overlapping of −ΔSM (T) around Tc1 and Tc2 induce a large refrigerant capacity (RC) within a large temperature range. The large reversible magnetocaloric effect (−ΔSMpeak ∼ 16 J/kg K for a field change of 0–5 T) and RC (=396 J/kg) indicate that TbMn2Si2 could be a promising candidate for low temperature magnetic refrigeration.
Publisher: Wiley
Date: 30-08-2019
DOI: 10.1111/JACE.16755
Abstract: BiFeO 3 ‐BaTiO 3 (BF‐BT) solid solutions are lead‐free candidates for high‐temperature piezoelectric applications. BF‐BT ceramics with compositions near the morphotropic phase boundary (MPB) separating rhombohedral (R) and pseudo‐cubic (PC) phases were fabricated by the conventional high temperature sintering method, and their thermal stability and aging properties were studied in detail. BF‐BT ceramics with rhombohedral (R) phase show much better thermal stability and aging properties than those with pseudo‐cubic (PC) or coexistence of PC and R phases. The thermal degradation and aging rates of BF‐BT ceramics with R phase are on the order of 1% and 1.2% per decade, respectively. X‐ray diffraction results reveal that the domain state of poled rhombohedral BF‐BT ceramics is stable up to its Curie temperature, which is responsible for the high thermal stability. The Rayleigh analysis shows that the low aging rate is attributed to the low domain wall contribution to the overall piezoelectric response. The high thermal stability and low aging rates indicate that the lead‐free BF‐BT ceramics with R phase are potential candidates for sensor and transducer applications over a broad temperature range.
Publisher: Elsevier BV
Date: 10-2022
Publisher: American Chemical Society (ACS)
Date: 12-02-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1TA10692A
Abstract: Multi-layered nanostructures obtained by Cu 2 Se achieve extremely low thermal conductivity in AgCuTe.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7TA09117F
Abstract: Remarkably improved thermoelectric properties are achieved through the synergetic effects of the resonance levels, the valence band convergence, and the carrier concentration optimization by chemical doping.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP03477H
Abstract: AgCuTe alloying introduces endotaxial nanostructures in SnTe, which significantly decrease thermal conductivity and enhance ZT .
Publisher: Wiley
Date: 16-08-2021
Abstract: As a promising candidate for the much‐desired low power consumption spintronic devices, 2D magnetic van der Waals material also provides a versatile platform for the design and control of topological spin textures. In this work on WTe 2 /CrCl 3 bilayer van der Waals heterostructures, a complete Néel‐type skyrmion–bimeron–ferromagnet phase transition is demonstrated, accompanied by the evolution of the topological number. This cyclic transition, mediated by a perpendicular magnetic field, is largely driven by the competition between the out‐of‐plane magnetocrystalline anisotropy and magnetic dipole–dipole interaction. In the presence of a driving current, the Néel‐type skyrmion gains a higher velocity yet larger skyrmion Hall angle, in comparison to the bimeron. By incorporating a ferroelectric CuInP 2 S 6 monolayer as a substrate, writing and erasing of skyrmions may be regulated using a ferroelectric polarization. This work sheds light on a novel approach to the design and control of magnetic skyrmions on 2D van der Waals materials.
Publisher: Springer Science and Business Media LLC
Date: 19-06-2015
DOI: 10.1038/SREP11288
Abstract: The structural and magnetic properties of seven CeMn 2 Ge 2-x Si x compounds with x = 0.0–2.0 have been investigated in detail. Substitution of Ge with Si leads to a monotonic decrease of both a and c along with concomitant contraction of the unit cell volume and significant modifications of the magnetic states - a crossover from ferromagnetism at room temperature for Ge-rich compounds to antiferromagnetism for Si-rich compounds. The magnetic phase diagram has been constructed over the full range of CeMn 2 Ge 2-x Si x compositions and co-existence of ferromagnetism and antiferromagnetism has been observed in CeMn 2 Ge 1.2 Si 0.8 , CeMn 2 Ge 1.0 Si 1.0 and CeMn 2 Ge 0.8 Si 1.2 with novel insight provided by high resolution neutron and X-ray synchrotron radiation studies. CeMn 2 Ge 2-x Si x compounds (x = 0, 0.4 and 0.8) exhibit moderate isothermal magnetic entropy accompanied with a second-order phase transition around room temperature. Analysis of critical behaviour in the vicinity of T C inter for CeMn 2 Ge 2 compound indicates behaviour consistent with three-dimensional Heisenberg model predictions.
Publisher: American Chemical Society (ACS)
Date: 06-05-2019
Abstract: Compounds that exhibit the unique behavior of negative thermal expansion (NTE)-the physical property of contraction of the lattice parameters on warming-can be applied widely in modern technologies. Consequently, the search for and design of an NTE material with operational and controllable qualities at room temperature are important topics in both physics and materials science. In this work, we demonstrate a new route to achieve magnetic manipulation of a giant NTE in (Mn
Publisher: American Chemical Society (ACS)
Date: 13-10-2014
DOI: 10.1021/NN5047585
Abstract: Although much progress has been made to develop high-performance lithium-sulfur batteries (LSBs), the reported physical or chemical routes to sulfur cathode materials are often multistep/complex and even involve environmentally hazardous reagents, and hence are infeasible for mass production. Here, we report a simple ball-milling technique to combine both the physical and chemical routes into a one-step process for low-cost, scalable, and eco-friendly production of graphene nanoplatelets (GnPs) edge-functionalized with sulfur (S-GnPs) as highly efficient LSB cathode materials of practical significance. LSBs based on the S-GnP cathode materials, produced by ball-milling 70 wt % sulfur and 30 wt % graphite, delivered a high initial reversible capacity of 1265.3 mAh g(-1) at 0.1 C in the voltage range of 1.5-3.0 V with an excellent rate capability, followed by a high reversible capacity of 966.1 mAh g(-1) at 2 C with a low capacity decay rate of 0.099% per cycle over 500 cycles, outperformed the current state-of-the-art cathode materials for LSBs. The observed excellent electrochemical performance can be attributed to a 3D "sandwich-like" structure of S-GnPs with an enhanced ionic conductivity and lithium insertion/extraction capacity during the discharge-charge process. Furthermore, a low-cost porous carbon paper pyrolyzed from common filter paper was inserted between the 0.7S-0.3GnP electrode and porous polypropylene film separator to reduce/eliminate the dissolution of physically adsorbed polysulfide into the electrolyte and subsequent cross-deposition on the anode, leading to further improved capacity and cycling stability.
Publisher: Elsevier BV
Date: 11-2013
Publisher: Wiley
Date: 29-11-2014
Publisher: AIP Publishing
Date: 15-12-2016
DOI: 10.1063/1.4971959
Abstract: The magnetocaloric effect is observed in the 1:1:1 compound ErRhSi, which is a metamagnet is reported in this paper. ErRhSi crystallizes in the orthorhombic space group Pnma, adopting the TiNiSi structure type, with lattice parameters a(Å) = 6.7903(5), b(Å) = 4.1881(3), and c(Å) = 7.3847(4). Our magnetic measurements confirm an antiferromagnetic phase transition at TN ≈ 8.5 K, also supported by the specific heat measurement. Crystal field effects of Er3+ are suggested by the inverse magnetic susceptibility data which do not conform to an ideal Curie-Weiss behaviour and also by the total entropy that attains Rln (2) at TN. Although the magnetic hysteresis indicates ErRhSi to be a soft magnet, several clear metamagnetic features are observed at 2 K. Magnetic entropy change ΔSM = − 8.7 J/kg-K is observed at about 9 K with the application of 5 T magnetic field. The corresponding adiabatic temperature change ΔTad is about 4 K. Large magnetocaloric effects suggest that this material is suitable for the low temperature magnetic refrigeration.
Publisher: AIP Publishing
Date: 07-03-2012
DOI: 10.1063/1.3677666
Abstract: The structural and magnetic properties of HoNi2Mn(57Fe) have been investigated. The 57Fe-doped HoNi2Mn compound crystallizes in the MgCu2-type structure with Fd-3m space group similar to HoNi2 and HoMn2. HoNi2Mn(57Fe) exhibits ferrimagnetic ordering below a Curie temperature of TC ∼ 60 K—significantly higher than the corresponding values for HoNi2 (TC = 15 K) and HoMn2 (TC = 24 K)—with analyses of dc magnetization and ac susceptibility results confirming that the magnetic transition at TC is second order. The Mössbauer spectra above TC are described well by two sub-spectra representing the 8a and 16d sites while below TC the spectra have been fitted using a site model comprising three sub-spectra. The Debye temperature, θD = 190(20) K, has been determined.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2011
Publisher: EDP Sciences
Date: 2014
Publisher: Elsevier BV
Date: 02-2019
Publisher: American Chemical Society (ACS)
Date: 08-2018
Publisher: Wiley
Date: 29-03-2017
Abstract: Rechargeable sodium-ion batteries are proposed as the most appropriate alternative to lithium batteries due to the fast consumption of the limited lithium resources. Due to their improved safety, polyanion framework compounds have recently gained attention as potential candidates. With the earth-abundant element Fe being the redox center, the uniform carbon-coated Na
Publisher: Wiley
Date: 26-08-2013
Publisher: Elsevier BV
Date: 11-2016
Publisher: AIP Publishing
Date: 13-02-2023
DOI: 10.1063/5.0136219
Abstract: Here, we report the growth of (Sr, Ca) Nd2Fe2O7 single crystals with the Ruddlesden–Popper structure using an optical floating-zone method. A significantly anisotropic magneto-dielectric effect (MD), ab-plane and c-axial MD coefficients reaching −12.3% and −8.4% measured at 103 Hz in a 1 T magnetic field, can be obtained in a SrNd2Fe2O7 crystal at room temperature. The corresponding anisotropic MD ratio can be reached as high as 1.46. With an increase in the Ca concentration, the MD effect decreases dramatically and is eventually completely suppressed in both directions. Analysis of magnetic properties and 57Fe Mössbauer spectra suggests that the anisotropic MD effects in SrNd2Fe2O7 can be attributed to polaronic hopping between two neighboring Fe3+ ions through oxygen vacancies in an anisotropically antiferromagnetic matrix the disappearance of the MD effect in Ca-doped SrNd2Fe2O7 is a consequence of the suppression of the antiferromagnetism. Our work suggests that the significantly anisotropic MD effect in SrNd2Fe2O7 crystals at room temperature can be used in magneto-dielectric controlled devices.
Publisher: Springer Science and Business Media LLC
Date: 06-2010
Publisher: IOP Publishing
Date: 29-03-2016
Publisher: AIP Publishing
Date: 05-02-2015
DOI: 10.1063/1.4907614
Abstract: The structural and magnetic properties of DyFe11.2Nb0.8 compound have been investigated by high intensity, high resolution synchrotron x-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements as well as Mössbauer spectroscopy (5–300 K). The easy magnetization direction at room temperature is along the c-axis. With decreasing temperature, the magnetocrystalline anisotropy changes from easy-axis to easy-cone at Tsr2 (∼202 K), then to easy plane at Tsr1 (∼94 K). The thermal expansion coefficient obtained from the synchrotron x-ray study exhibits clear anomalies around both of the spin reorientation transition temperatures. The 57Fe hyperfine interaction parameters and magnetic moments values have been determined for the 8i, 8j, and 8f sites from the Mössbauer spectra.
Publisher: Elsevier BV
Date: 03-2022
Publisher: American Physical Society (APS)
Date: 04-06-2013
Publisher: IOP Publishing
Date: 09-05-2011
DOI: 10.1088/0953-8984/23/21/216002
Abstract: The structural and magnetic properties of the TbNi(2)Mn(x) series (0.9 ≤ x ≤ 1.10) have been investigated using x-ray diffraction, field- and temperature-dependent AC magnetic susceptibility, DC magnetization (5-340 K 0-5 T) and (57)Fe Mössbauer spectroscopy (5-300 K). TbNi(2)Mn(x) crystallizes in the MgCu(2)-type structure (space group Fd3m). The additional contributions to the magnetic energy terms from transition-metal-transition-metal interactions (T-T) and rare-earth-transition-metal interactions (R-T) in RNi(2)Mn compounds contribute to their increased magnetic ordering temperatures compared with RNi(2) and RMn(2). Both the lattice constant a and the Curie temperature T(C) exhibit maximal values at the x = 1 composition indicating strong magnetostructural coupling. Analyses of the AC magnetic susceptibility and DC magnetization data of TbNi(2)Mn around the Curie temperature T(C) = 147 K confirm that the magnetic transition is second order with critical exponents β = 0.77 ± 0.12, γ = 1.09 ± 0.07 and δ = 2.51 ± 0.06. These exponents establish that the magnetic interactions in TbNi(2)Mn are long range despite mixed occupancies of Tb and Mn atoms at the 8a site and vacancies. The magnetic entropy - ΔS(M) around T(C) is proportional to (μ(0)H/T(C))(2/3) in agreement with the critical magnetic analyses. The Mössbauer spectra above T(C) are fitted by two sub-spectra in agreement with refinement of the x-ray data while below T(C) three sub-spectra are required to represent the three inequivalent local magnetic environments.
Publisher: AIP Publishing
Date: 18-03-2011
DOI: 10.1063/1.3535544
Abstract: Investigation of ErNi2Mnx with 0.90 ≤ x ≤ 1.10 indicates that the MgCu2-type structure (with space group Fd-3m) is formed within x = 0.97−1.10. Curie temperature TC = 50 K of ErNi2Mn is significantly higher than those of the corresponding ErNi2 (TC = 7 K) and ErMn2 (TC = 15 K) compounds. Detailed analyses of DC magnetization data demonstrate that the magnetic phase transition at the Curie temperature is second order. The magnetic entropy change around TC has been found to be 4.8 J/kg K for a magnetic field change of 0 to 5 T with its relative cooling power ∼283 J/kg. 57Fe Mössbauer spectra below TC have been fitted with three sub-spectra representing three inequivalent local magnetic environments while the paramagnetic spectra are fitted using two sub-spectra for two inequivalent crystal sites (8a and 16d), which supports the conclusion based on Rietveld refinement that Mn atoms occupy at both 8a and 16d sites.
Publisher: AIP Publishing
Date: 05-09-2016
DOI: 10.1063/1.4962465
Abstract: We studied the temperature dependent magnetic phase evolution in spin frustrated TbMnO3 affected by Fe doping via powder neutron diffraction. With the introduction of Fe (10% and 20%), the long range incommensurate magnetic orderings collapse. When the Fe content is increased to 30%, a long-range antiferromagnetic ordering develops, while a spin reorientation transition is found near 35 K from a canted G-type antiferromagnetic ordering to a collinear G-type antiferromagnetic ordering. This work demonstrates the complex magnetic interactions existing in transition metal oxides, which helps to understand the frustrated spin states in other similar systems and design magnetic materials as well.
Publisher: MDPI AG
Date: 29-01-2022
Abstract: The critical behaviour associated with the field-induced martensitic transformation heavily relies on the vacancy and transition of the magnetic phase in MnCoGe based-compounds. Due to this revelation, an intensive investigation was brought forth to study the substitution of Ge (atomic radius = 1.23 Å) by Al (atomic radius = 1.43 Å) in MnCoGe0.97Al0.03 alloy compound. The room-temperature X-ray diffraction indicated that the reflections were identified with the orthorhombic structure (TiNiSi-type, space group Pnma) and minor hexagonal structure (Ni2In-type, space group P63/mmc). The substitution of Al in the supersession of Ge transmuted the crystal structure from TiNiSi-type to Ni2In-type structure. The MnCoGe0.97Al0.03 compound’s magnetism was driven by interactions that are long in range, as indicated by the study of the critical behaviour in the proximity of TC. The magnetic measurement and neutron diffraction revealed that the structural transition took place with the decrease in temperature. The results from neutron diffraction signify that the transformation of the magnetic field-induced martensitic has a crucial function in producing the immense effect of magnetocaloric systems such as these. This outcome serves a critical function for investigations in the future.
Publisher: AIP Publishing
Date: 04-2011
DOI: 10.1063/1.3565401
Abstract: In an effort to improve the magnetocaloric effects of the NaZn13-type La0.8Ce0.2Fe11.4Si1.6 compound, the effect of boron doping on the magnetic properties and magnetocaloric properties has been investigated. The magnetic entropy change (ΔSM) for the La0.8Ce0.2Fe11.4Si1.6 compound, obtained for a field change of 0–5 T using the Maxwell relation exhibits a spike and appears to be overestimated and is thus corrected by using the Clausius-Clapeyron equation (CC). The ΔSM determined from the CC equation is estimated to be 19.6 J kg−1K−1. However, large hysteretic losses which are detrimental to the magnetic refrigeration efficiency occur in the same temperature range. In this work, we report a significant reduction in hysteretic losses by doping the La0.8Ce0.2Fe11.4Si1.6 compound with a small amount of boron to obtain La0.8Ce0.2Fe11.4Si1.6Bx compounds. The hysteresis loss decreases from 131.5 to 8.1 J kg −1 when x increases from 0 to 0.3, while ΔSM, obtained for a field change of 0–5 T, varies from 19.6 to 15.9 J kg−1K−1. This also simultaneously shifts the TC from 174 to 184 K and significantly improves the effective refrigerant capacity (RCeff) of the material from 164 to 305 J kg−1.
Publisher: IOP Publishing
Date: 02-2008
Publisher: IOP Publishing
Date: 16-10-2013
Publisher: Springer Science and Business Media LLC
Date: 14-11-2014
Publisher: Springer Science and Business Media LLC
Date: 26-11-2013
Publisher: IOP Publishing
Date: 29-08-2013
DOI: 10.1088/0953-8984/25/38/386003
Abstract: The structural and magnetic properties of seven PrMn2Ge2-xSix compounds with Si concentrations in the range x = 0.0-2.0 have been investigated by x-ray diffraction, magnetic (5-350 K), differential scanning calorimetry (300-500 K) and neutron diffraction (3-480 K) measurements. Replacement of Ge by Si leads to a contraction of the unit cell and significant modifications to the magnetic states--a crossover from ferromagnetism at room temperature for Ge-rich compounds to antiferromagnetism for Si-rich compounds. The compositional dependence of the room temperature lattice parameters exhibits non-linear behaviour around x = 1.2, reflecting the presence of magnetovolume effects. Re-entrant ferromagnetism has been observed in both PrMn2Ge1.0Si1.0 and PrMn2Ge0.8Si1.2 compounds with co-existence of canted ferromagnetism and canted antiferromagnetism detected, with both compounds exhibiting a larger unit cell volume in the canted Fmc state than in the canted AFmc. Combined with earlier studies of this system, the magnetic phase diagram has been constructed over the full range of PrMn2Ge2-xSix compositions (x = 0.0-2.0) and over the temperature range of interest (T = 3-480 K). In common with other systems in the RMn2X2 series, the overall magnetic behaviour of PrMn2Ge2-xSix compounds is governed by the strong dependence of the magnetic couplings on the Mn-Mn spacing within the ab-plane. Both total manganese moment µ(Mn)(tot) and in-plane manganese moment µ(Mn)(ab) at 5 K are found to decrease with increasing Si content, which can be ascribed to the reduction of Mn-Mn separation distance and stronger Si-Mn hybridization compared with Ge-Mn hybridization. Pr site ferromagnetic ordering occurs for x < 1.6 below T(Pr)(C).
Publisher: Wiley
Date: 26-03-2014
Publisher: AIP Publishing
Date: 03-04-2014
DOI: 10.1063/1.4868703
Abstract: In an effort to explore the effect of substitution Fe by Cr in NaZn13-type La0.7Pr0.3Fe11.4−xCrxSi1.6 (x = 0, 0.06, 0.12, 0.26, and 0.34) compounds, the structure and magnetic properties have been investigated by high intensity of x-ray and neutron diffraction, scanning electron microscopy, specific heat, and magnetization measurement. It has been found that a substitution of Cr for Fe in this compounds leads to decrease in the lattice parameter a at room temperature but variation on Curie temperature (TC). While the first order nature of magnetic phase transition around TC does not change with increasing Cr content up to x = 0.34. High intensity x-ray and neutron diffraction study at variable temperatures for highest Cr concentration x = 0.34 confirmed the presence of strong magneto-volume effect around TC and indicated the direct evident of coexistence across magnetic transition as characteristic of first order nature. The values of −ΔSM around TC decrease from 17 J kg−1 K−1 for x = 0 to 12 J kg−1 K−1 for x = 0.06 and then increases with further increasing Cr content up to 17.5 J kg−1 K−1 for x = 0.34 under a change of 0–5 T magnetic field. Similar behavior on relative cooling power which is decrease from 390 J kg−1 for x = 0 to 365 J kg−1 for x = 0.06 at the beginning and then increases up to 400 J kg−1 for x = 0.34. From the point of this view with the highest Cr concentration (x = 0.34) exhibits favourable material candidate for magnetic refrigerator application therefore should inspire further study concerning on higher Cr concentration in this compound.
Publisher: Springer Science and Business Media LLC
Date: 09-02-2021
DOI: 10.1038/S41467-021-21202-7
Abstract: (K,Na)NbO 3 based ceramics are considered to be one of the most promising lead-free ferroelectrics replacing Pb(Zr,Ti)O 3 . Despite extensive studies over the last two decades, the mechanism for the enhanced piezoelectricity in multi-elements doped (K,Na)NbO 3 ceramics has not been fully understood. Here, we combine temperature-dependent synchrotron x-ray diffraction and property measurements, atomic-scale scanning transmission electron microscopy, and first-principle and phase-field calculations to establish the dopant–structure–property relationship for multi-elements doped (K,Na)NbO 3 ceramics. Our results indicate that the dopants induced tetragonal phase and the accompanying high-density nanoscale heterostructures with low-angle polar vectors are responsible for the high dielectric and piezoelectric properties. This work explains the mechanism of the high piezoelectricity recently achieved in (K,Na)NbO 3 ceramics and provides guidance for the design of high-performance ferroelectric ceramics, which is expected to benefit numerous functional materials.
Publisher: Wiley
Date: 26-03-2014
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