磁场诱导的TmFeO_(3)单晶自旋重取向

Magnetic-field-induced spin reorientation in TmFeO_(3) single crystals

TmFeO_(3)具有磁光效应、多铁性和自旋重取向等丰富的物理特性,在凝聚态物理和材料物理领域具有重要的研究价值.本文利用时域太赫兹低温磁光谱,研究TmFeO_(3)单晶在1.6 K温度下自旋共振频率随外加磁场的变化规律,并表征其内部复杂的相互作用.结果表明,随磁场增加TmFeO_(3)单晶的准铁磁共振向高频移动,而准反铁磁共振在临界磁场(2.2—3.6 T)转变为准铁磁共振,通过磁结构分析和理论拟合,证实单晶磁矩发生了磁场诱导的自旋重取向.本研究有助于深入理解稀土正铁氧体在外磁场、温度场综合作用下,内部磁结构的调控机制,开发相关的自旋电子学器件.

TmFeO_(3) exhibits rich physical properties such as magneto-optical effect,multiferroicity,and spin reorientation,making it possess significant research value in condensed matter physics and materials science.In this study,we utilize a time-domain terahertz magneto-optical spectroscopy system to investigate the changes in spin resonance frequency of TmFeO_(3) single crystal at T = 1.6 K under external magnetic fields in a range of 0–7 T.The TmFeO_(3) sample is grown in an optical floating zone furnace and its crystallographic orientation is determined by using back-reflection Laue X-ray photography with a tungsten target.The measurement setup is a self-built time-domain terahertz magneto-optical spectroscopy system,with magnetic fields in a range of 0–7 T,temperatures in a range of 1.6–300 K,and a spectral range of 0.2–2.0 THz.A pair of 1 mm-thick ZnTe nonlinear crystals is used to generate and detect terahertz signals through optical rectification and electro-optic sampling technique.The system variable temperature and magnetic field are controlled by a superconducting magnet.In experiments,a linearly polarized terahertz wave is vertically incident on the sample surface,and its magnetic component HTHz is parallel to the sample surface.By rotating the sample,the angle(θ) between macroscopic magnetic moment M and HTHz can be tuned,achieving selective excitations of the two modes,that is,θ = 0 for q-AFM mode and 90° for q-FM mode.Terahertz absorption spectrum results indicate that as the magnetic field increases,the quasi-ferromagnetic resonance(q-FM) of TmFeO_(3) single crystal shifts towards high frequencies,and quasi-antiferromagnetic resonance(q-AFM) transits to q-FM under low critical magnetic fields(2.2–3.6 T).Through magnetic structure analysis and theoretical fitting,it is confirmed that the magnetic moment of the single crystal undergoes magnetic field induced spin reorientation.This study is helpful in better understanding of the regulation mechanism of the internal magnetic structure of rare earth ferrite under the combined action of external magnetic field and temperature field,and also in developing related spin electronic devices.