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Magnetic-order induced effects in nanocrystalline NiO probed by Raman spectroscopy
Physical Review B ( IF 3.2 ) Pub Date : 
Nisha Bala, H. K. Singh, Shikha Verma, Shyama Rath

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:

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^ {-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。
更新日期:2020-07-03
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