Abstract Polycrystalline Ni0.48Cu0.12Zn0.40GdxFe2-xO4 (where x = 0.00, 0.02, 0.04, 0.08, and 0.10) was synthesized by the conventional solid-state reaction technique. The structure and surface morphology were studied by X-ray diffraction (XRD) and high-resolution optical microscopy, respectively. The XRD patterns indicated that the compositions formed a cubic spinel structure for a small amount of Gd3+ substitution. With increasing Gd3+ concentration, a gradual rise in the intensity of the extra peaks was observed, and those peaks were identified as corresponding to GdFeO3 (orthoferrite). Rietveld refinement was performed on the XRD data of Gd3+-substituted Ni0.48Cu0.12Zn0.40 ferrite samples for further verification, and the results were found to be in good agreement with results reported in the literature. Variation of the lattice constant obeyed Vegard's law. Microstructural studies showed that the average grain diameter increases as the Gd3+ content increases up to an optimum concentration and then it decreases. Magnetic properties were characterized by the complex initial permeability (100 Hz–100 MHz). The real part of the complex initial permeability ( μ i ′ ) increases with Gd3+ concentration up to x = 0.04 and then decreases. Ni0.48Cu0.12Zn0.40Gd0.04Fe1.96O4 shows the highest value of μ i ′ (at the optimum sintering temperature), which is more than eight times that of the parent sample. Conversely, magnetic loss is reduced remarkably in this composition. The Neel temperature was determined from the temperature-dependent initial complex permeability, which showed a decreasing trend with increase in Gd3+ concentration owing to the weakening of the A-B interaction. DC magnetizations as a function of the applied magnetic field were evaluated with a vibrating-sample magnetometer at room temperature. The magnetization increased with increasing Gd3+ content up to x = 0.04 owing to the variation of cation distribution and then reduced because of the possibility of noncollinear spin arrangement with further increase of Gd3+ content. The number of Bohr magnetons (nB) and the Yaffet-Kittel angle (αY-K) were evaluated. The calculated αY-K values were a minimum for x = 0.04, while the nB variation showed the opposite trend. Because of the reduction of electron exchanges between Fe2+ and Fe3+ at the octahedral site, the room temperature dielectric constant and the dielectric loss were reduced with increasing Gd3+ content. There was an exceptional increase in the dielectric constant for x = 0.02 sample. The AC conductivity spectrum exhibited two regions, and the conductivity was found to decrease with the addition of Gd3+. Impedance spectroscopy studies indicated a non-Debye-type relaxation process. Ferroelectric transition temperatures, TC, were also determined from measurement of the temperature-dependent dielectric constant.

中文翻译：

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Gd3+ 取代的 Ni-Cu-Zn 混合铁氧体的晶体学、磁学和电学性能

摘要 多晶 Ni0.48Cu0.12Zn0.40GdxFe2-xO4（其中 x = 0.00、0.02、0.04、0.08 和 0.10）是通过常规固相反应技术合成的。分别通过X射线衍射（XRD）和高分辨率光学显微镜研究了结构和表面形貌。XRD图谱表明组合物形成了少量Gd3+取代的立方尖晶石结构。随着 Gd3+ 浓度的增加，观察到额外峰的强度逐渐增加，这些峰被确定为对应于 GdFeO3（正铁氧体）。对 Gd3+ 取代的 Ni0.48Cu0.12Zn0.40 铁氧体样品的 XRD 数据进行 Rietveld 细化以进一步验证，发现结果与文献报道的结果非常吻合。晶格常数的变化遵循 Vegard 定律。微观结构研究表明，平均晶粒直径随着 Gd3+ 含量增加到最佳浓度而增加，然后又减少。磁特性的特征在于复杂的初始磁导率（100 Hz–100 MHz）。复数初始渗透率的实部 (μ i ' ) 随 Gd3+ 浓度增加至 x = 0.04，然后减小。Ni0.48Cu0.12Zn0.40Gd0.04Fe1.96O4 的μ i '值最高（在最佳烧结温度下），是母体样品的八倍多。相反，在该组合物中磁损耗显着降低。Neel 温度由依赖于温度的初始复合渗透率确定，由于 AB 相互作用减弱，随着 Gd3+ 浓度的增加而呈下降趋势。在室温下用振动样品磁力计评估作为外加磁场函数的直流磁化强度。由于阳离子分布的变化，磁化强度随着 Gd3+ 含量的增加而增加，直到 x = 0.04，然后由于随着 Gd3+ 含量的进一步增加而出现非共线自旋排列的可能性而降低。评估了玻尔磁子数 (nB) 和 Yaffet-Kittel 角 (αY-K)。计算出的 αY-K 值是 x = 0.04 的最小值，而 nB 变化显示出相反的趋势。由于八面体位点Fe2+和Fe3+之间的电子交换减少，室温介电常数和介电损耗随着 Gd3+ 含量的增加而降低。x = 0.02 样品的介电常数有异常增加。交流电导率谱呈现出两个区域，发现电导率随着 Gd3+ 的加入而降低。阻抗谱研究表明非德拜型弛豫过程。铁电转变温度 TC 也通过测量与温度相关的介电常数来确定。