Department of Physics, Ewha Womans University, Seoul 03760, South Korea.
Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, South Korea.
Spectrochim Acta A Mol Biomol Spectrosc. 2023 Sep 5;297:122700. doi: 10.1016/j.saa.2023.122700. Epub 2023 Apr 1.
Nanostructured antiferromagnetic (AFM) NiO has attracted much attention from both the fundamental and applied perspectives. Understanding the two-magnon (2 M) is of great significance in NiO applications such as spin valves and next-generation magnetic random access memories (MRAM). We investigated the phonon modes and antiferromagnetically ordered states of NiO nanoparticles prepared by empirically controlled measurements. An intensity enhancement of the 2 M mode was observed by Raman spectroscopy as the NiO nanoparticles were vacuum annealed at 650 ℃. The increased 2 M peak intensity in NiO nanoparticles is explained by the local symmetry conversions from NiO to NiO configurations due to the oxygen redistribution during the vacuum annealing. The change of the splitting of anisotropic transverse optical (TO) phonon with different oxygen contents was also revealed by the Raman spectroscopy. We have shown that the changes in the oxygen environment underlie both the change in the 2 M intensity and the splitting of TO phonon in the NiO nanoparticles. Our work offers an efficient avenue to strengthen the AFM ordering and emphasizes the effect of vacuum annealing of the NiO nanoparticles, opening the interesting possibility of individual parameter control in practical applications.
具有纳米结构的反铁磁（AFM）NiO 从基础和应用的角度都引起了极大的关注。了解双磁子（2M）对于 NiO 在自旋阀和下一代磁随机存取存储器（MRAM）等应用中具有重要意义。我们通过经验控制的测量来研究纳米 NiO 颗粒的声子模式和反铁磁有序状态。通过拉曼光谱观察到，当 NiO 纳米颗粒在 650℃下真空退火时，2M 模式的强度增强。由于真空退火过程中氧的重新分布，NiO 转变为 NiO 构型导致局部对称转换，从而解释了 NiO 纳米颗粒中 2M 峰强度的增加。拉曼光谱还揭示了不同氧含量下各向异性横向光学（TO）声子分裂的变化。我们已经表明，氧环境的变化是 NiO 纳米颗粒中 2M 强度变化和 TO 声子分裂的基础。我们的工作为增强 AFM 有序提供了一种有效的途径，并强调了 NiO 纳米颗粒真空退火的影响，为实际应用中的单个参数控制开辟了有趣的可能性。
