The Nano-crystalline divalent copper ion substituted Ni–Zn ferrites having chemical formula Ni_0.5Zn_0.5−xCu_xFe₂O₄ (where x = 0.05 to 0.25 in steps of 0.05) were prepared by citrate gel auto-combustion method. The X-ray diffraction study confirmed the single phase spinel cubic structure and the crystallographic studies indicate that the lattice parameter was observed to be decreased with increasing of Cu²⁺ concentration. Scanning Electron Microscopy was conducted to observe surface morphology and grain size/shape. Magnetic measurements were carried out using Vibrating Sample Magnetometer for magnetization and Impedance analyzer for permeability up to 15 MHz. Magnetization studies revealed that the incorporation of copper into the system modified the exchange interactions leading to gradual decrease in saturation magnetization. Highest saturation magnetization was observed for the base composition Ni_0.5Zn_0.5CuFe₂O₄ with 61 emu/g. There was an increase in coercivity and remanence with copper concentration. Frequency and temperature variation of inductance measurements were performed to understand the system behaviour at different threshold limits. Enhancement of initial permeability was observed up to the concentration x = 0.15 and its variation is observed to be grain size dependent. Temperature variation of permeability leads to Curie temperature, which was increased with increasing of Cu²⁺ concentration. All magnetic characteristics of the present system of nano crystalline ferrites displayed interesting deviations and reasons were well justified.

中文翻译：

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柠檬酸-凝胶法合成Cu 2+取代的Ni-Zn纳米晶铁氧体的磁性

采用柠檬酸盐凝胶自动燃烧法制备了化学式为Ni _0.5 Zn _0.5-x Cu _x Fe ₂ O ₄（其中x = 0.05至0.25，步长为0.05）的纳米晶二价铜离子取代的Ni-Zn铁氧体。X射线衍射研究证实了单相尖晶石立方结构，晶体学研究表明，随着Cu ^2+的增加，晶格参数降低。专注。进行扫描电子显微镜观察表面形态和晶粒尺寸/形状。使用用于磁化的振动样品磁力计和用于高达15 MHz的磁导率的阻抗分析仪进行磁测量。磁化研究表明，将铜结合到系统中可以改变交换相互作用，从而导致饱和磁化强度逐渐降低。观察到基本成分Ni _0.5 Zn _0.5 CuFe ₂ O _4的最高饱和磁化强度含61 emu / g。矫顽力和剩磁随铜浓度的增加而增加。进行电感测量的频率和温度变化以了解系统在不同阈值限制下的行为。直至浓度x = 0.15，初始磁导率都得到增强，并且观察到其变化与晶粒尺寸有关。渗透率的温度变化导致居里温度，居里温度随着Cu ²⁺浓度的增加而增加。本系统的纳米晶铁氧体的所有磁特性都显示出有趣的偏差，并且其原因是合理的。