Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208106, India.
J Phys Condens Matter. 2011 Nov 9;23(44):445403. doi: 10.1088/0953-8984/23/44/445403.
Temperature dependent x-ray diffraction and Raman spectroscopic studies were carried out on flux-grown single crystals of gallium ferrite with a Ga:Fe ratio of 0.9:1.1. Site occupancy calculations from the Rietveld refinement of the x-ray data led to an estimated magnetic moment of ~0.60 μ(B)/f.u. which was in good agreement with the experimental data. A combination of these two measurements indicates that there is no structural phase transition in the material between 18 and 700 K. A detailed line shape analysis of the Raman mode at ~374 cm(-1) revealed a discontinuity in the peak position data indicating the presence of spin-phonon coupling in gallium ferrite. A correlation of the peak frequency with the magnetization data led to two distinct regions across a temperature ~180 K with appreciable change in the spin-phonon coupling strength from ~0.9 (T < 180 K) to 0.12 cm(-1) (180 K < T < T(c)). This abrupt change in the coupling strength at ~180 K strongly suggests an altered spin dynamics across this temperature.
采用熔融提拉法生长出 Ga:Fe 比为 0.9:1.1 的 Ga 铁氧体单晶，对其进行了温度依赖的 X 射线衍射和拉曼光谱研究。根据 X 射线数据的 Rietveld 精修，对晶体占位进行了计算，得出的估算磁矩约为 0.60 μ(B)/f.u.，与实验数据吻合较好。这两种测量结果表明，在 18 至 700 K 之间，材料中没有结构相变。对约 374 cm(-1)处的拉曼模的精细线谱分析表明，在峰位数据中存在不连续性，表明 Ga 铁氧体中存在自旋-声子耦合。峰频率与磁化数据的相关性表明，在温度约 180 K 处存在两个明显的区域，自旋-声子耦合强度从约 0.9（T < 180 K）显著变化到 0.12 cm(-1)（180 K < T < T(c)）。在约 180 K 时，耦合强度的这种突然变化强烈表明，在该温度范围内，自旋动力学发生了改变。
