The temperature evolution of the LiNiPO4 single crystal Raman spectra in a region of 2–25 K, which includes a phase transition to a magnetically ordered state, is studied. For the first time, magnetic contribution in the Raman spectra was divided into single-magnon and two-magnon excitations at 2 K. The energies of the detected single-magnon excitations are in good agreement with the data obtained earlier from transmission spectra in the near-IR region. The shape of the two-magnon scattering band corresponds to the published data for the density of two-magnon states. A shift in some phonon lines was detected in the transition to a magnetically ordered state, which indicates a significant magnon-phonon interaction. A change in the scattering spectrum intensities below TN was observed, which depends on the polarization of the incident light. It is suggested that this effect is associated with a shift of the Ni2+-ion absorption bands during magnetic ordering in the region of the 532 nm excitation line. This indicates a significant interaction between the electronic and magnetic subsystems in the crystal under study.

中文翻译：

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LiNiPO4 单晶磁相变过程中的拉曼散射

研究了 LiNiPO4 单晶拉曼光谱在 2-25 K 范围内的温度演变，其中包括向磁有序状态的相变。拉曼光谱中的磁贡献首次在 2 K 处分为单磁振子激发和双磁振子激发。检测到的单磁振子激发的能量与早先从近场透射光谱中获得的数据非常吻合。 -红外区域。双磁振子散射带的形状对应于已公布的双磁振子态密度数据。在向磁有序状态的转变过程中检测到一些声子线的变化，这表明存在显着的磁子-声子相互作用。观察到低于 TN 的散射光谱强度的变化，这取决于入射光的偏振。有人认为，这种效应与 532 nm 激发线区域磁有序期间 Ni2+-离子吸收带的移动有关。这表明所研究的晶体中的电子和磁性子系统之间存在显着的相互作用。