DyFeO_(3)中高于Morin温度的新型磁相变  

A new magnetic phase transition above Morin temperature in DyFeO_(3)

作　　者：苏浩斌 郑世芸 王宁 朱国锋 居学尉 黄峰 曹义明 王向峰 SU Haobin;ZHENG Shiyun;WANG Ning;ZHU Guofeng;JU Xuewei;HUANG Feng;CAO Yiming;WANG Xiangfeng(Fujian Provincial Key Laboratory of Terahertz Functional Devices and Intelligent Sensing,School of Mechanical Engineering and Automation,Fuzhou University,Fuzhou 350108,China;School of Physics and Electronic Engineering,Qujing Normal University,Qujing 655011,China;Pen-Tung Sah Institute of Micro-Nano Science and Technology,Xiamen University,Xiamen 361102,China)

机构地区：[1]福州大学机械工程及自动化学院,福建省太赫兹功能器件与智能传感重点实验室,福州350108 [2]曲靖师范学院物理与电子工程学院,曲靖655011 [3]厦门大学,萨本栋微米纳米科学技术研究院,厦门361102

出　　处：《物理学报》2025年第8期247-253,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:62105068);福建省自然科学基金(批准号:2023J05096,2023J01055);福建省太赫兹功能器件与智能传感重点实验室(福州大学)开放基金(批准号:FPKLTFDIS202304);福建省教育厅中青年教师教育科研项目(批准号:JAT220032)资助的课题.

摘　　要：稀土正铁氧体(RFeO_(3),R为稀土原子)包含Fe^(3+)和R^(3+)两套磁性离子亚晶格,存在Fe^(3+)-Fe^(3+),Fe^(3+)-R^(3+),R^(3+)-R^(3+)三种相互作用,它们是稀土正铁氧体丰富磁性的来源.本文利用时域太赫兹磁光谱,在1.6—300 K的温度范围内,在不同磁场下,测量a-cut DyFeO_(3)单晶样品的吸收光谱,并分析光谱中铁磁(FM)和反铁磁共振(AFMR)吸收峰的温度和磁场依赖特性.在零磁场变温实验中,我们发现随温度降低在Morin温度(~50 K)出现的温度诱导的自旋重取向(Γ_(4)→Γ_(1)),以及在4 K温度以下存在一个由于电磁振子导致的宽带吸收.在Morin温度以上,我们在恒定温度(70,77,90,100 K)下测量了样品在0—7 T磁场范围的吸收光谱.实验结果表明,随着磁场的增大,存在一个新的磁相变过程(Γ_(4)→Γ_(24)→Γ_(2)→Γ_(24)→Γ_(2)),相变的临界磁场随温度而变化.这一相变过程是由于外磁场和Fe^(3+)-Dy^(3+)的各向异性交换相互作用导致的内部有效场的相互竞争和对磁矩的协同作用.本项研究为深入理解稀土铁氧化物的丰富相变和磁电耦合特性,以及开发相关的自旋电子学器件提供参考.Rare-earth orthoferrites(RFeO_(3))have received significant attention due to their intricate magnetic interactions and potential applications in ultrafast spintronic devices.Among them,DyFeO_(3)exhibits rich magnetic phase transitions driven by the interplay between Fe^(3+)and Dy^(3+)sublattices.Previous studies mainly focused on temperature-induced spin reorientation near the Morin temperature(TM~50 K),but there has been limited exploration of magnetic phase behavior under external fields above TM.This work aims to systematically investigate the temperature-and magnetic-field-dependent magneto-dynamic properties of a-cut DyFeO_(3)single crystals,with an emphasis on identifying novel phase transitions and elucidating the underlying mechanisms involving Fe^(3+)-Dy^(3+)anisotropic exchange interactions.High-quality a-cut DyFeO_(3)single crystals are grown using the optical floating zone method and characterized by X-ray diffraction(XRD)and Laue diffraction.Time-domain terahertz spectroscopy(THz-TDS)coupled with a superconducting magnet(0–7 T,1.6–300 K)is employed to probe the ferromagnetic resonance(FM)and antiferromagnetic resonance(AFMR)modes.By analyzing the frequency trends in the spectra,the response of internal magnetic moments to external stimuli can be inferred.In the zero magnetic field experiment,it is found that the temperature induced spin reorientation(Γ_(4)→Γ_(1))occurs at Morin temperature(~50 K)with temperature decreasing.A broadband electromagnetic absorption(0.45–0.9 THz)occurs below 4 K,which is attributed to electromagnons activated by broken inversion symmetry in the Dy^(3+)antiferromagnetic state.Above the Morin temperature,the absorption spectra of the sample are measured at constant temperatures(70,77,90,100 K)and magnetic fields ranging from 0 to 7 T.The experimental results show that with the increase of magnetic field,a new magnetic phase transition occurs(Γ_(4)→Γ_(24)→Γ_(2)→Γ_(24)→Γ_(2)),and the critical magnetic field of the phase transition varies with temperatur

关 键 词：稀土正铁氧体 太赫兹 磁共振 磁相变 

分 类 号：O482.5[理学—固体物理]