摘要
本文通过实验系统研究了Heusler合金Co_(2)FeAl_(x)Si_(1-x)(x=0,0.25,0.5,0.75,1)体系中原子占位有序度与磁致伸缩的关联机制.研究发现,Al掺杂可导致体系从高度有序的L21结构向B2无序结构转变,并在x=0.25—0.5时诱导L2_(1)/B2两相共存界面态的形成,此时有序度计算结果显示S_(L21)/SB2=0.5—0.9.实验结果表明,这种界面态的出现显著增强了饱和磁致伸缩系数并在过渡到B2结构后再次减小.该结果定量揭示了原子的局部无序占位可通过降低立方对称性、引入局域晶格畸变并改变磁畴结构,从而提升磁弹耦合的物理机制.本研究报道了12种Co基Heusler合金的磁致伸缩系数,其中Co_(2)MnGa和Co_(2)CrGa展现出优于其他Co基Heusler合金的潜力,填补了该体系磁致伸缩性能参数的空白,并验证了该多晶材料的线性正磁致伸缩特性;提出了基于原子占位有序度调控的磁致伸缩性能优化策略,为开发耐高温、高自旋极化率的磁致伸缩材料提供了新方向.
Co-based Heusler alloys have emerged as highly promising systems within the Heusler alloy family due to their high Curie temperatures and potential half-metallicity.Since the concept of half-metallic ferromagnets is proposed,these alloys have attracted significant attention because of their high spin polarization,excellent magnetic performance,and thermal stability.The existing studies predominantly focus on spin-transport properties,but systematic studies on their magnetostriction remain scarce.The electronic structure and magnetism of Co-based Heusler alloys are critically dependent on atomic-site ordering:their spin polarization,Curie temperature,and magnetocrystalline anisotropy are closely related to crystal structure,such as L2_(1)and B2.A highly ordered L2_(1)structure is essential for maintaining half-metallicity,as structural disorder can induce significant changes in electronic hybridization and exchange interactions,thereby significantly changing macroscopic magnetism.Additionally,ordering control is also expected to modulate magnetostriction by modifying lattice symmetry and local distortions.Notably,in Fe-Ga alloys,disorder engineering has been employed to induce local short-range order and lattice distortion,thereby enhancing magnetostriction,a mechanism that may similarly operate in Co-based systems.However,the higher lattice symmetry and stronger orbital hybridization in these alloys can lead to fundamentally distinct mechanisms,which needs to be validated experimentally.This study focuses on the Co_(2)FeAl_(x)Si_(1-x)system to systematically probe the relationship between composition-driven structural evolution(i.e.,L2_(1)to B2 transition)and magnetostrictive performance through adjusting Al/Si ratio.The study aims to clarify the correlation between composition-induced structural evolution and magnetostrictive behavior,thereby revealing the regulatory role of atomic ordering in magnetoelastic coupling and providing theoretical insight for designing high-performance magnetostrictive materials.The correlation between atomic site ordering and magnetostriction in Heusler alloy Co_(2)FeAl_(x)Si_(1-x)(x=0,0.25,0.5,0.75,1)is systematically investigated in experiment.The results reveal that Al doping drives a structural transition from the highly ordered L2_(1)phase to the disordered B2 phase,inducing a coexisting L2_(1)/B2 interface state at x=0.25-0.5,with the calculated ordering parameters ranging from 0.5 to 0.9.The experimental data demonstrate that this interface state significantly enhances the saturation magnetostriction coefficient(λs),which subsequently decreases as it further transitions to the B2-dominated structure.These findings quantitatively clarify the physical mechanism by which local atomic disorder enhances magnetoelastic coupling through reducing cubic symmetry,localizing lattice distortion,and changing magnetic domain configuration.Furthermore,this study reports for the first time the magnetostriction coefficients of 12 Co-based Heusler alloys,among which Co_(2)MnGa and Co_(2)CrGa exhibit superior potential compared with other Co based Heusler alloys,filling the gap in magnetostriction performance parameters of this system.The linear positive magnetostriction behaviors of the polycrystalline materials are also validated.This study provides a strategy for optimizing magnetostriction performance through atomic site ordering control,and points out a new direction for the development of magnetostrictive materials with high-temperature stability and high spin polarization.
作者
姚亮
芦光辉
杜杰
刘永昌
郗学奎
王文洪
YAO Liang;LU Guanghui;DU Jie;LAU Yongchang;XI Xuekui;WANG Wenhong(School of Electronics and Information Engineering,Tiangong University,Tianjin 300387,China;Institute of Physics,Chinses Academy of Sciences,Beijing 100190,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《物理学报》
北大核心
2025年第14期289-298,共10页
Acta Physica Sinica
基金
国家重点研发计划(批准号:2021YFB3501402,2024YFF0726703)
国家自然科学基金(批准号:12274321,12361141823)资助的课题。
