Abstract Mn substituted Ni-Zn mixed ferrites doped with Gd3+ ions belonging to the series Mn0.2Ni0.6Zn0.2GdxFe2-xO4 (x=0.00, 0.02, 0.04, 0.06) have been synthesized by sol-gel method. The effect of Gd3+ substitution on the structural, cationic distribution, magnetic and dielectric properties has been investigated in detail. X-Ray analysis reveals formation of single phase spinel cubic ferrite nanoparticles with no secondary phases. The average crystallite size estimated using Scherrer’s relation lie in the 11–13 nm range with the size decreasing with increase in Gd ion content. Lattice constants calculated from proposed cation distribution are in close agreement with reported values. Surface morphology studies using SEM and HRTEM show spherical shaped nanoparticles which are slightly agglomerated. EDX analysis confirms the expected stoichiometry. The valence state of materials was characterized by XPS. The dielectric variations with frequency and temperature were analyzed using a precision impedance analyzer. The relative permittivity and dielectric loss show an increasing trend with Gd concentration up to x=0.04 and then decrease with further increase in doping. Increasing the temperature increases the relative permittivity. Measurements of magnetic parameters using VSM were performed at room temperature and at 77K. M−H loops recorded have shown that the synthesized ferrite nanoparticles exhibit soft ferrimagnetism. The saturation magnetization and coercivity decrease with increase in Gd doping. The samples possess high magnetization and coercivity at low temperatures. A remarkable difference in the magnetic moments estimated from measured magnetic parameters and from the cation distribution over A and B sites on the basis of Neel’s two sublattice model of ferrimagnetism was noted in all the samples. Higher Y-K angles obtained imply their potential use in synthesis of magnetoresistive (MR) materials.

中文翻译：

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用于磁阻应用的掺杂 Gd 离子的 Mn 取代 Ni-Zn 混合铁氧体增强的低温磁性能

摘要 采用溶胶-凝胶法合成了Mn0.2Ni0.6Zn0.2GdxFe2-xO4 (x=0.00, 0.02, 0.04, 0.06)系列的掺杂Gd3+离子的Mn取代Ni-Zn混合铁氧体。已经详细研究了 Gd3+ 取代对结构、阳离子分布、磁性和介电性能的影响。X 射线分析表明形成了没有第二相的单相尖晶石立方铁氧体纳米颗粒。使用 Scherrer 关系估计的平均微晶尺寸在 11-13 nm 范围内，尺寸随着 Gd 离子含量的增加而减小。从建议的阳离子分布计算的晶格常数与报告值非常一致。使用 SEM 和 HRTEM 的表面形态研究显示球形纳米颗粒略微聚集。EDX 分析证实了预期的化学计量。材料的价态通过 XPS 表征。使用精密阻抗分析仪分析电介质随频率和温度的变化。相对介电常数和介电损耗随 Gd 浓度增加至 x=0.04 呈增加趋势，然后随着掺杂的进一步增加而降低。增加温度会增加相对介电常数。使用 VSM 测量磁参数是在室温和 77K 下进行的。记录的 M-H 环表明合成的铁氧体纳米粒子表现出软亚铁磁性。饱和磁化强度和矫顽力随着Gd掺杂的增加而降低。样品在低温下具有高磁化强度和矫顽力。在所有样品中都注意到根据测量的磁参数和 A 和 B 位点上的阳离子分布估计的磁矩存在显着差异，这是基于 Neel 的亚铁磁性的两个亚晶格模型。获得的更高 YK 角意味着它们在合成磁阻 (MR) 材料中的潜在用途。