Investigating the antiferromagnetic transitions of TbFe₃(BO₃)₄ and GdFe₃(BO₃)₄ by soft X-ray absorption spectroscopies

Yi-Ying Chin^1*, Ping-Yi Wang¹, Ruei Tze Hung¹, Hong-Ji Lin², Chien-Te Chen², Hiroshi Nakajima³, Tsuyoshi Kimura⁴, Ashish Chainani²

¹Department of Physics, National Chung Cheng University, Chiayi, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan
³Department of Materials Science, Osaka Prefecture University, Osaka, Japan
⁴Department of Advanced Materials Science, University of Tokyo, Chiba, Japan

* Presenter:Yi-Ying Chin, email:yiyingchin@ccu.edu.tw

The RM₃(BO₃)₄ series, where R represents rare-earth metals or Y and M represents Al, Ga, and Fe, is an intriguing multiferroic system distinguished by its non-centrosymmetric trigonal structure. This unique system has a wide spectrum of physical properties resulting from the interactions between rare-earth 4f electrons and metal 3d electrons. For instance, RFe₃(BO₃)₄ is in an antiferromagnetic (AFM) phase at low temperatures. Neutron diffraction experiments have confirmed the presence of the AFM transition with Neel temperatures falling between 30 K and 40 K. Those studies demonstrated the dominant role of Fe in the AFM behavior. Notably, various AFM structures, including easy-axis and easy-plane, have been observed, underscoring the crucial role of R ions in shaping the AFM behavior.

Utilizing linearly polarized light, specifically X-ray linear dichroism (XLD), enables the exploration of orbital anisotropy arising from both structural distortion and magnetic interactions. In this study, XLD experiments were conducted on single crystals of TbFe₃(BO₃)₃ and GdFe₃(BO₃)₄. The results unveiled modifications in the Fe-L_2,3 spectra across the AFM phase transition. Furthermore, a distinction in the Fe XLD between TbFe₃(BO₃)₄ and GdFe₃(BO₃)₄ was observed, aligning with their unique AFM structures. Additionally, the magnetization enhancement in TbFe₃(BO₃)₄ owing to an external magnetic field was investigated by using X-ray magnetic circular dichroism (XMCD). By combining the XMCD data with the configuration-interaction cluster calculations, the orientation of Fe and Tb moments was determined. These findings shed light on the intricate interplay of magnetic interactions in the RFe₃(BO₃)₄ multiferroic system.

Keywords: Antiferromagnetic phase transition, X-ray linear dichroism, X-ray magnetic circular dichroism, Multiferroic