Four Sm_(2)Co_(17)magnets with spin-reorientation transition(SRT)of cell boundary phases(CBPs)are prepared by liquid-phase sintering.The temperature of the SRT of CBPs(T_(SR)^(1:5))is regulated from 125 K to 195 K by ...Four Sm_(2)Co_(17)magnets with spin-reorientation transition(SRT)of cell boundary phases(CBPs)are prepared by liquid-phase sintering.The temperature of the SRT of CBPs(T_(SR)^(1:5))is regulated from 125 K to 195 K by adding 0 wt.%,3 wt.%,6 wt.%and 9 wt.%Dy_(88)Cu_(12)alloy powder.The effect of SRT of Sm_(2)Co_(17)magnet CBPs on the temperature dependence of the magnetization(M-T)and coercivity(H-T)is systematically investigated.The temperature dependence of the magnetization is influenced by the SRT of CBPs.The M-T curves measured during the heating process are larger than those measured during the cooling process when T<T_(SR)^(1:5).When T=T_(SR)^(1:5)there is a bifurcation point.When T>T_(SR)^(1:5)the M-T curves overlap and the M-T derivation curve shows that the magnetization of the magnet has low temperature dependence of magnetization above T_(SR)^(1:5).With increasing T_(SR)^(1:5),the initial temperature of the low temperature dependence of magnetization shifts towards a higher temperature.The coercivity temperature coefficient becomes positive as the SRT effect increases,and the temperature range of the positive coercivity temperature coefficient moves towards higher temperatures as T_(SR)^(1:5)increases.This reveals that SRT of CBPs has little effect on the temperature dependence of magnetization above T_(SR)^(1:5),while the temperature dependence of coercivity is optimized.The temperature range of magnetization and coercivity with low temperature dependence tends towards higher temperatures,which is conducive to the preparation of magnets with a low temperature coefficient at higher temperatures.展开更多
Polycrystalline BiFeO3 and rare earth substituted Bio.gRo.lFeO3 （BRFO, R=Y, Ho and Er） compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds sta...Polycrystalline BiFeO3 and rare earth substituted Bio.gRo.lFeO3 （BRFO, R=Y, Ho and Er） compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds stabilized in rhombohedral structure （R3c space group） and a small orthorhombic phase fraction was observed in BRFO compounds. From the Raman spectra results, the changes in the phonon frequencies （A1） and line widths suggested lattice distortion in the BRFO compounds as was evidenced in the XRD analysis. Compared to the linear variation of magnetization with magnetic field （M-H） shown by BFO, an obvious M-H loop was observed in BRFO compounds which could be due to the suppression of space modulated spin structure and was explained on the basis of weak ferromagnetism and field induced spin reorientation. UV-Vis spectroscopy evidenced a change in local FeO6 envi- ronment due to shift in the 6Alg→4T2g energy transition band. BRFO compounds with improved remnant magnetization and coercive field are applicable for magnetoelectric devices.展开更多
We report microstructure,magnetocaloric effect and thermal transfer properties of highly orientated Nd0.8Pr0.2Co5 alloy prepared by powder metallurgical processing.Two spin-reorientation transitions of easy magnetizat...We report microstructure,magnetocaloric effect and thermal transfer properties of highly orientated Nd0.8Pr0.2Co5 alloy prepared by powder metallurgical processing.Two spin-reorientation transitions of easy magnetization direction,easy plane to easy cone at TSR1=206 K,easy cone to easy axis at TSR2=242 K,are observed.The present textured alloy exhibits a rotating entropy change of 2.6 J/(kg·K)and refrigerant capacity of 155 J/kg under a magnetic field of 2 T,and high thermal conductivity of 11 W/(m·K).The sintered Nd0.8Pr0.2Co5 alloy with good combination of excellent magnetocaloric and thermal transfer properties are promising for scientific research and practical applications as room-temperature rotating magnetic refrigeration materials.展开更多
Polycrystallines Bi0.5Ca0.5-xLaxFe0.3Mn0.7O3（x=0, 0,05, 0.10, 0.15, 0.20, 0.25） were prepared by molten salt method and showed perovskite orthorhombic structure with space group Pnma. The magnetic measurements indic...Polycrystallines Bi0.5Ca0.5-xLaxFe0.3Mn0.7O3（x=0, 0,05, 0.10, 0.15, 0.20, 0.25） were prepared by molten salt method and showed perovskite orthorhombic structure with space group Pnma. The magnetic measurements indicate that the compounds exhibit antiferromagnetic behavior in a temperature range of 4-300 K. The measurements of transport properties suggest that the substitution of La for Ca enhanced the conductivity, and a kink appeared on the curve of temperature dependence of resistivity at 275 K, which is related to the spin-reorientation in the samples.展开更多
Topologically protected magnetic skyrmions are expected to be used in the next-generation spintronic devices.Realizing their nucleation and manipulation at room temperature is fundamental for future practical applicat...Topologically protected magnetic skyrmions are expected to be used in the next-generation spintronic devices.Realizing their nucleation and manipulation at room temperature is fundamental for future practical applications.Here,using in situ Lorentz transmission electron microscopy and micromagnetic simulation,we demonstrate that magnetic biskyrmions can spontaneously exist at room temperature in Nd_(1-x) Tb_(x)Co_(5)(x=0.3,0.5)alloys.The spontaneous biskyrmions are controllably obtained over a wide temperature range across room temperature by switching atomic chemical environment.Furthermore,the density of biskyrmions can be tuned by a small magnetic field.High-density biskyrmions are stimulated to form in the thinner region at room temperature by introducing an in-plane magnetic field component.These results provide valuable insights into the manipulation of topological states,which is of great significance to their practical applications.展开更多
The magnetostriction, magnetization, and spin reorientation properties in Pr(Ga_(x)Fe_(1-x))_(1.9) alloys have been investigated by high-precision x-ray diffraction(XRD) step scanning, magnetization, and Mossbauer spe...The magnetostriction, magnetization, and spin reorientation properties in Pr(Ga_(x)Fe_(1-x))_(1.9) alloys have been investigated by high-precision x-ray diffraction(XRD) step scanning, magnetization, and Mossbauer spectra measurements. Ga substitution reduces the magnetostriction(λ_(||)) with magnetic field H ≥ 8 kOe(1 Oe = 1.33322×10^(2) Pa), but it also increases the λ|| value when H ≤ 8 kOe at 5 K. Spin-reorientations(SR) are observed in all the alloys investigated, as determined by the step scanned XRD, Mossbauer spectra, and the abnormal temperature dependence of magnetization. An increase of the spin reorientation temperature(T_(SR)) due to Ga substitution is found in the phase diagram, which is different from the decrease one in many R(T_(x) Fe_(1-x))_(1.9)(T = Co, Al, Mn) alloys. The present work provides a method to control the easy magnetization direction(EMD) or T_(SR) for developing an anisotropic compensation system.展开更多
the spin-reorientation transition from out-of-plane to in-plane in Fe/Si film is widely reported, the tuning of in-plane spin orientation is not yet well developed. Here, we report the thickness-, temperature- and Cu-...the spin-reorientation transition from out-of-plane to in-plane in Fe/Si film is widely reported, the tuning of in-plane spin orientation is not yet well developed. Here, we report the thickness-, temperature- and Cu-adsorptioninduced in-plane spin-reorientation transition processes in Fe/Si （557） film, which can be attributed to the coexistence of two competing step-induced uniaxial magnetic anisotropies, i.e., surface magnetic anisotropy with magnetization easy axis perpendicular to the step and volume magnetic anisotropy with magnetization easy axis parallel to the step. For Fe film thickness smaller than 32 monolayer （ML）, the magnitudes of two effects under various temperatures are extracted from the thickness dependence of uniaxial magnetic anisotropy. For Fe film thickness larger than 32 ML, the deviation of experimental results from fitting results is understood by the strain-relief-induced reduction of volume magnetic anisotropy. Additionally, the surface and volume magnetic anisotropies are both greatly reduced after covering Cu capping layer on Fe/Si （557） film while no significant influence of NaC1 capping layer on step-induced magnetic anisotropies is observed. The experimental results reported here provide various practical methods for manipulating in-plane spin orientation of Fe/Si films and improve the understanding of step-induced magnetic anisotropies.展开更多
基金Project supported by the National Key R&D Program of China (Grant Nos.2021YFB3803003 and 2021YFB3503101)Youth Innovation Promotion Association of CAS (Grant No.2023311)+1 种基金Major Project of‘Science and Technology Innovation 2025’in Ningbo (Grant No.2020Z044)Zhejiang Provincial Key Research and Development Program (Grant No.2021C01172)。
文摘Four Sm_(2)Co_(17)magnets with spin-reorientation transition(SRT)of cell boundary phases(CBPs)are prepared by liquid-phase sintering.The temperature of the SRT of CBPs(T_(SR)^(1:5))is regulated from 125 K to 195 K by adding 0 wt.%,3 wt.%,6 wt.%and 9 wt.%Dy_(88)Cu_(12)alloy powder.The effect of SRT of Sm_(2)Co_(17)magnet CBPs on the temperature dependence of the magnetization(M-T)and coercivity(H-T)is systematically investigated.The temperature dependence of the magnetization is influenced by the SRT of CBPs.The M-T curves measured during the heating process are larger than those measured during the cooling process when T<T_(SR)^(1:5).When T=T_(SR)^(1:5)there is a bifurcation point.When T>T_(SR)^(1:5)the M-T curves overlap and the M-T derivation curve shows that the magnetization of the magnet has low temperature dependence of magnetization above T_(SR)^(1:5).With increasing T_(SR)^(1:5),the initial temperature of the low temperature dependence of magnetization shifts towards a higher temperature.The coercivity temperature coefficient becomes positive as the SRT effect increases,and the temperature range of the positive coercivity temperature coefficient moves towards higher temperatures as T_(SR)^(1:5)increases.This reveals that SRT of CBPs has little effect on the temperature dependence of magnetization above T_(SR)^(1:5),while the temperature dependence of coercivity is optimized.The temperature range of magnetization and coercivity with low temperature dependence tends towards higher temperatures,which is conducive to the preparation of magnets with a low temperature coefficient at higher temperatures.
基金supported by Department of Science and Technology (DST),Government of India under Fast Track Scheme (SR/FTP/PS-065/2011)
文摘Polycrystalline BiFeO3 and rare earth substituted Bio.gRo.lFeO3 （BRFO, R=Y, Ho and Er） compounds were prepared by rapid solid state sintering technique. Structural phase analysis indicated that all the compounds stabilized in rhombohedral structure （R3c space group） and a small orthorhombic phase fraction was observed in BRFO compounds. From the Raman spectra results, the changes in the phonon frequencies （A1） and line widths suggested lattice distortion in the BRFO compounds as was evidenced in the XRD analysis. Compared to the linear variation of magnetization with magnetic field （M-H） shown by BFO, an obvious M-H loop was observed in BRFO compounds which could be due to the suppression of space modulated spin structure and was explained on the basis of weak ferromagnetism and field induced spin reorientation. UV-Vis spectroscopy evidenced a change in local FeO6 envi- ronment due to shift in the 6Alg→4T2g energy transition band. BRFO compounds with improved remnant magnetization and coercive field are applicable for magnetoelectric devices.
基金the National Natural Science Foundation of China(51601208,51531008,51601209)the Fujian Institute of Innovation,Chinese Academy of Sciences(FJCXY18040301)。
文摘We report microstructure,magnetocaloric effect and thermal transfer properties of highly orientated Nd0.8Pr0.2Co5 alloy prepared by powder metallurgical processing.Two spin-reorientation transitions of easy magnetization direction,easy plane to easy cone at TSR1=206 K,easy cone to easy axis at TSR2=242 K,are observed.The present textured alloy exhibits a rotating entropy change of 2.6 J/(kg·K)and refrigerant capacity of 155 J/kg under a magnetic field of 2 T,and high thermal conductivity of 11 W/(m·K).The sintered Nd0.8Pr0.2Co5 alloy with good combination of excellent magnetocaloric and thermal transfer properties are promising for scientific research and practical applications as room-temperature rotating magnetic refrigeration materials.
基金Supported by the National Natural Science Foundation of China(Nos90922034, 20771042)
文摘Polycrystallines Bi0.5Ca0.5-xLaxFe0.3Mn0.7O3（x=0, 0,05, 0.10, 0.15, 0.20, 0.25） were prepared by molten salt method and showed perovskite orthorhombic structure with space group Pnma. The magnetic measurements indicate that the compounds exhibit antiferromagnetic behavior in a temperature range of 4-300 K. The measurements of transport properties suggest that the substitution of La for Ca enhanced the conductivity, and a kink appeared on the curve of temperature dependence of resistivity at 275 K, which is related to the spin-reorientation in the samples.
基金supported by the Science Center of the Na-tional Science Foundation of China(Grant No.52088101)the Na-tional Natural Science Foundation of China(Grant Nos.52121001,52001019,52271195,52101210,and 52130103)+2 种基金the National Key and Development Program of China(Grant Nos.2021YFB3501600,2022YFB3505302)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDB33030100,XDB33030200)Youth Innovation Promotion Association(No.CAS Y201903).
文摘Topologically protected magnetic skyrmions are expected to be used in the next-generation spintronic devices.Realizing their nucleation and manipulation at room temperature is fundamental for future practical applications.Here,using in situ Lorentz transmission electron microscopy and micromagnetic simulation,we demonstrate that magnetic biskyrmions can spontaneously exist at room temperature in Nd_(1-x) Tb_(x)Co_(5)(x=0.3,0.5)alloys.The spontaneous biskyrmions are controllably obtained over a wide temperature range across room temperature by switching atomic chemical environment.Furthermore,the density of biskyrmions can be tuned by a small magnetic field.High-density biskyrmions are stimulated to form in the thinner region at room temperature by introducing an in-plane magnetic field component.These results provide valuable insights into the manipulation of topological states,which is of great significance to their practical applications.
基金supported by the National Natural Science Foundation of China (Grant No. 51901052)the Science Foundation of Guangxi Zhuang Autonomous Region,China (Grant No. 2018GXNSFAA281294)the Training Programme for Thousands of Core Teachers in Guangxi Zhuang Autonomous Region,China。
文摘The magnetostriction, magnetization, and spin reorientation properties in Pr(Ga_(x)Fe_(1-x))_(1.9) alloys have been investigated by high-precision x-ray diffraction(XRD) step scanning, magnetization, and Mossbauer spectra measurements. Ga substitution reduces the magnetostriction(λ_(||)) with magnetic field H ≥ 8 kOe(1 Oe = 1.33322×10^(2) Pa), but it also increases the λ|| value when H ≤ 8 kOe at 5 K. Spin-reorientations(SR) are observed in all the alloys investigated, as determined by the step scanned XRD, Mossbauer spectra, and the abnormal temperature dependence of magnetization. An increase of the spin reorientation temperature(T_(SR)) due to Ga substitution is found in the phase diagram, which is different from the decrease one in many R(T_(x) Fe_(1-x))_(1.9)(T = Co, Al, Mn) alloys. The present work provides a method to control the easy magnetization direction(EMD) or T_(SR) for developing an anisotropic compensation system.
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB921403 and 2016YFA0300701)the National Natural Sciences Foundation of China(Grant Nos.51427801,11374350,11274360,and 11274361)
文摘the spin-reorientation transition from out-of-plane to in-plane in Fe/Si film is widely reported, the tuning of in-plane spin orientation is not yet well developed. Here, we report the thickness-, temperature- and Cu-adsorptioninduced in-plane spin-reorientation transition processes in Fe/Si （557） film, which can be attributed to the coexistence of two competing step-induced uniaxial magnetic anisotropies, i.e., surface magnetic anisotropy with magnetization easy axis perpendicular to the step and volume magnetic anisotropy with magnetization easy axis parallel to the step. For Fe film thickness smaller than 32 monolayer （ML）, the magnitudes of two effects under various temperatures are extracted from the thickness dependence of uniaxial magnetic anisotropy. For Fe film thickness larger than 32 ML, the deviation of experimental results from fitting results is understood by the strain-relief-induced reduction of volume magnetic anisotropy. Additionally, the surface and volume magnetic anisotropies are both greatly reduced after covering Cu capping layer on Fe/Si （557） film while no significant influence of NaC1 capping layer on step-induced magnetic anisotropies is observed. The experimental results reported here provide various practical methods for manipulating in-plane spin orientation of Fe/Si films and improve the understanding of step-induced magnetic anisotropies.
