Ho1–xYxFeO3单晶自旋重取向的掺杂效应与磁控效应的太赫兹光谱  

Terahertz spectroscopy study of doping and magnetic field induced effects on spin reorientation in Ho1-xYxFeO3 single crystals

作　　者：任壮 成龙 谢尔盖·固瑞特斯基[3] 那泽亚·柳博奇科 李江涛 尚加敏 谢尔盖·巴里洛 武安华 亚历山大·卡拉什尼科娃[5] 马宗伟 周春 盛志高 Ren Zhuang;Cheng Long;Sergei Guretskii;Nadzeya Liubochko;Li Jiang-Tao;Shang Jia-Min;Sergei Barilo;Wu An-Hua;Alexandra Kalashnikova;Ma Zong-Wei;Zhou Chun;Sheng Zhi-Gao(High Magnetic Field Laboratory,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,China;University of Science and Technology of China,Hefei 230026,China;Scientific-Practical Materials Research Centre of NAS of Belarus,Minsk 220072,Belarus;Shanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai 200050,China;Ioffe Technologies Institute,St.Petersburg 194021,Russia)

机构地区：[1]中国科学院合肥物质科学研究院,强磁场科学中心,合肥230031 [2]中国科学技术大学,合肥230026 [3]白俄罗斯国家航空航天局,科学实用材料研究中心,明斯克220072 [4]中国科学院上海硅酸盐研究所,上海200050 [5]俄罗斯约飞技术研究所,圣·彼得堡194021

出　　处：《物理学报》2020年第20期119-127,共9页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2016YFA0401803,2017YFA0303603);中国科学院前沿科学重点研究项目(批准号:QYZDB-SSWSLH011);国家自然科学基金(批准号:11574316,51872309,61805256,11904367,U1832106,52011530018);中国科学院俄乌白特别交流计划;上海市科委科技基金(批准号:19520710900);白俄罗斯-中国研究框架中的白俄罗斯基础研究基金(批准号:F20CN-021)资助的课题.

摘　　要：利用自研的磁场下太赫兹时域光谱(terahertz time-domain spectroscopy,THz-TDS),系统研究了磁场与非磁性Y3+离子掺杂对HoFeO3单晶中自旋态以及自旋重取向的影响.结果表明Y3+掺杂可以在不改变自旋重取向类型情况下,有效降低自旋重取向温区,而且还能降低Ho1–xYxFeO3单晶中低温区准铁磁模式(q-FM,quasi-ferromagnetic mode)自旋共振频率以及提升高温区的准反铁磁模式(q-AFM,quasi-antiferromagnetic mode)自旋共振频率.在沿(110)方向施加外加磁场(HDC)的情况下,一方面,发现磁场不仅能有效调控Ho1–xYxFeO3单晶中的q-FM共振频率,而且还能诱导出自旋重取向;另一方面,发现温度越接近自旋重取向温区时,磁诱导自旋重取向的发生越容易,而且磁诱导效应的临界磁场强度随Y3+离子掺杂浓度而增加.研究表明,THz光谱数据可以用于检测HoFeO3中Y3+离子的掺杂浓度,而且Y3+掺杂可以使HoFeO3晶体中的自旋态更加稳定,不容易受外界磁场的影响.这一自旋重取向的掺杂效应、磁控效应的研究将有助于理解稀土正铁氧体中的自旋交换作用及其外场调控机制.In this paper,the effects of magnetic field and nonmagnetic Y3+doping on spin state and spin reorientation in HoFeO3 single crystal are systematically studied by the self-developed terahertz time-domain spectroscopy(THz-TDS)under magnetic field.By doping nonmagnetic Y3+,we find that the spin reorientation temperature range decreases.Meanwhile,we also find the type of spin reorientation of HoFeO3 does not change with Y3+doping,indicating that the Y3+doping can exchange the interaction energy of Ho3+-Fe3+without introducing any new magnetic structure.Moreover,the resonance frequency of quasi-ferromagnetic mode(q-FM)decreases with temperature increasing in the low temperature range,while the resonance frequency of quasiantiferromagnetic mode(q-AFM)increases with temperature increasing in the high temperature range in Ho1–xYxFeO3 single crystals.With the external magnetic field(HDC)applied along the(110)axis,on the one hand the magnetic field can not only tune the resonant frequency of q-FM but also induce the spin reorientation in Ho1–xYxFeO3 single crystals,and on the other hand this magnetic field induced spin reorientation phenomenon can happen more easily if the temperature approaches to the intrinsic spin reorientation temperature range of the single crystals.Besides,the critical magnetic field induced spin reorientation increases with the doping of Y3+increasing.Our research shows that THz spectroscopy data can be used to detect the doping concentration of Y3+ions in HoFeO3;in addition,Y3+doping can make the spin state in HoFeO3 crystal more stable and not easily affected by external magnetic fields.We anticipate that the role of doping and magnetic field in spin reorientation transition will trigger great interest in understanding the mechanism of the spin exchange interaction and the mechanism of external field tuning effect in the vast family of rare earth orthoferrites.

关 键 词：太赫兹时域光谱 稀土正铁氧体 自旋重取向 自旋共振 

分 类 号：O433.5[机械工程—光学工程]