ABSTRACT Nickel ferrite nanocrystalline particles were prepared by hydrothermal method. A systematic study was carried out on their structural and magnetic properties in wide ranges of temperatures and magnetic fields. The prepared nanoparticles were investigated by XRD, TEM, FTIR, and VSM. The results of Rietveld refinement revealed that the nanoparticles have a cubic single phase spinel type structure. The TEM measurements showed that the nanoparticles were monodisperse and spherical in shape. The FTIR results confirmed the single phase nature of the prepared nanoparticles. The magnetic measurements showed that the nanoparticles were ferromagnetic over a wide temperature range. The saturation magnetisation and the first anisotropy constant were observed to increase with reducing temperature. The estimated size of a single magnetic domain was found to be around 13 nm, which is three times smaller than the estimated crystallite size found from XRD, confirming that the average size of the nanoparticles was located above the critical size of the single-domain regime.

中文翻译：

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探索接近单畴区尺寸上限的小结晶镍铁氧体纳米颗粒的结构和磁性能

摘要 采用水热法制备了镍铁氧体纳米晶颗粒。系统研究了它们在广泛的温度和磁场范围内的结构和磁性。通过XRD、TEM、FTIR和VSM研究了制备的纳米颗粒。Rietveld 精修结果表明纳米颗粒具有立方单相尖晶石型结构。TEM 测量表明纳米颗粒是单分散的和球形的。FTIR 结果证实了所制备纳米颗粒的单相性质。磁性测量表明纳米颗粒在很宽的温度范围内是铁磁性的。观察到饱和磁化强度和第一各向异性常数随着温度的降低而增加。