The magnetic-order induced effects in nanocrystalline NiO are investigated through the phonons and magnons observed in the Raman spectra The key observations are (i) an anisotropy of the first-order transverse and longitudinal optical phonons, with a splitting of the order of 5 meV and (ii) a marked size and excitation wavelength variation of the two- magnon (2M) peak, which varies linearly with a red-shift of $$50cm$^{-1}$ with a size reduction from 105 nm to 30 nm. The magnon related peaks, in contrast to the phonons, are suppressed for near-resonance laser excitations. The experimental results are interpreted in terms of the exchange interactions and strong electron-electron correlations. The magnetization measurements shows a crossover to ferromagnetism with large coercivities and magnetization with decreasing size, which is shown to be due to the thermo-induced contribution.

中文翻译：

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拉曼光谱探测纳米晶NiO中的磁序诱导效应

通过拉曼光谱中观察到的声子和磁振子研究了纳米晶NiO中的磁阶感应效应。主要观察结果是（i）一阶横向和纵向光学声子的各向异性，其分裂为5 meV。 （ii）两磁子（2M）峰的明显大小和激发波长变化，其随$的红移线性变化$50C米$^ {-1} $，尺寸从105 nm减小到30 nm。与声子相反，与磁振子有关的峰被抑制用于近共振激光激发。用交换相互作用和强电子-电子相关性解释了实验结果。磁化强度的测量结果显示，铁磁具有大的矫顽力，而磁化强度却减小，这表明是由于热感应作用引起的。