A series of Mg-doped NiFe2O4 (NMF) and Co-doped NiFe2O4 (NCF) nanoparticles were synthesized via citrate-gel method. The X-ray diffraction patterns of conventionally heated NMF and NCF nanoparticles confirmed the formation of single-phase cubic spinel structures. Further, the variation of structural parameters as a function of compositions was described. The morphology of NMF and NCF materials was investigated using scanning and transmission electron microscopes (SEM and TEM). In addition, the formation of tetrahedral (A-site) and octahedral (B-site) locations of NMF and NCF was obtained from the Fourier transform infrared spectra (FTIR). Furthermore, the room- and low-temperature magnetic properties were studied for NMF and NCF nanoparticles using magnetization versus magnetic field (M-H) loops and zero field cooled (ZFC) and field cooled (FC) curves, respectively. The results revealed that NMF and NCF nanoparticles exhibited superparamagnetic (SPM) nature at room temperature.

中文翻译：

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柠檬酸盐凝胶法合成纳米 NiXFe2O4 (X = Mg/Co)：结构、形态和低温磁性能

通过柠檬酸盐凝胶法合成了一系列Mg掺杂的NiFe2O4（NMF）和Co掺杂的NiFe2O4（NCF）纳米颗粒。常规加热的 NMF 和 NCF 纳米粒子的 X 射线衍射图证实了单相立方尖晶石结构的形成。此外，描述了作为组成函数的结构参数的变化。使用扫描和透射电子显微镜（SEM 和 TEM）研究了 NMF 和 NCF 材料的形貌。此外，NMF和NCF的四面体（A位）和八面体（B位）位置的形成是从傅里叶变换红外光谱（FTIR）获得的。此外，分别使用磁化与磁场 (MH) 回路以及零场冷却 (ZFC) 和场冷却 (FC) 曲线研究了 NMF 和 NCF 纳米粒子的室温和低温磁性。结果表明，NMF 和 NCF 纳米粒子在室温下表现出超顺磁性 (SPM) 性质。