Pr掺杂DyFeO3体系的自旋重取向相变、晶格畸变与Raman光谱研究

利用固相反应法制备了Dy_1-xPr_xFeO₃系列化合物. X射线粉末衍射晶体结构分析表明, 随着Pr掺杂量x的增加, 样品晶胞体积逐渐增大, 晶格畸变减弱. Raman光谱测量表明稀土离子有效质量m_eff=xm_Pr+(1-x)m_Dy] 与晶格结构的变化共同导致该体系Raman光谱的变化. 随Pr掺杂量的增加, 波数小于200 cm^-1的振动模式基本保持不变, 而波数大于200 cm^-1的振动模式(除420 cm^-1处的B_3u模式外)向低频移动. 磁测量结果表明, 由Dzyaloshinsky-Moriya 相互作用导致的宏观磁性随Pr掺杂量增加逐渐减弱. 稀土离子与铁离子磁晶格的耦合作用以及晶格结构畸变的变化共同导致该体系自旋重取向相变温度在一定的掺杂量 (x=0.3)前后先升高后降低. 关键词： 稀土铁氧体 自旋重取向 晶体结构 Raman光谱

The study of Raman spectrum,distortion of lattice and spin reorientation phase transition on Pr doped DyFeO3 system

Pr doped rare-earth orthoferrites DyFeO₃ is synthesized by solid state reaction. X-ray diffraction shows that the lattice parameters of Dy_1-xPr_xFeO₃increase and distortion of lattice decreases with Pr content x increasing. Raman spectroscopy reveals that the change of effective mass (m_eff) m_eff=xm_Pr+(1-x)m_Dy] together with lattice structure change results in the shift of vibration modes. With the increase of Pr content, Raman modes of wave number less than 200 cm^-1 remain constant, but the modes of wave number greater than 200 cm^-1 decrease with Pr content increasing (except the mode B_3u near 420 cm^-1). The weak ferromagnetic ordering, created by Dzyaloshinsky-Moriya interaction, is reduced with doping level increasing. The interaction of rare earth ions with Fe³⁺ ion, together with the change of lattice distortion, results in the increasing of spin reorientation phase transition temperature when x<0.3 and then decreasing with Pr content increasing x increasing to over 0.3.
Keywords： rare-earth orthoferrites spin reorientation lattice distortion Raman spectrum