Abstract In the present work, was studied the effect of the La3+ cation solubility on the structural, magnetic and electrical properties of M-type barium hexaferrite (BaM). The Rietveld refinement revealed changes in the lattice parameters with increasing the La3+ concentration. Variations in the bond length and the distortion index of 2b, 4f2 and 12k oxygen polyhedral were observed with the La3+ insertion in the BaM structure. In addition to the BaM phase, secondary phases Fe2O3 and LaFeO3 arise, whose concentrations depend on the La3+ solubility. The magnetic properties are strongly affected by the La3+ incorporation in the structure, as well as by the secondary phases. Changes in the oxidation state of Fe3+ to Fe2+ decreases the exchange interaction, resulting in the magnetic moments disturbance. The electrical properties are dependent on the La3+ content and the secondary phase concentration. Undoped sample present the highest impedance values, decreasing linearly in all frequency range. For doped samples, the resistivity decreases in several orders due to the La3+ incorporation, while the ac-conductivity remains constant at low frequencies and presents dispersion at high frequencies. The dielectric permittivity present space charge polarization mechanism generated by electron hopping from Fe3+ to Fe2+ ions. The Non-Debye-type relaxation and the conductivity transition of long and short range are suggested from the results of imaginary impedance and electric module. The bond valence model revealed that the most affected crystallographic sites are 2b, 4f2 and 12k, where the exchange of valence of Fe3+ by Fe2+ ions should take place.

中文翻译：

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La3+ 阳离子溶解度对六铁酸钡结构、磁性和电学性能的影响

摘要 在目前的工作中，研究了 La3+ 阳离子溶解度对 M 型六铁酸钡 (BaM) 结构、磁学和电学性能的影响。Rietveld 精修揭示了随着 La3+ 浓度的增加，晶格参数发生了变化。观察到在 BaM 结构中插入 La3+ 时，2b、4f2 和 12k 氧多面体的键长和变形指数发生了变化。除了 BaM 相之外，还会出现第二相 Fe2O3 和 LaFeO3，它们的浓度取决于 La3+ 的溶解度。磁性能受结构中 La3+ 的结合以及第二相的强烈影响。Fe3+ 到 Fe2+ 的氧化态变化降低了交换相互作用，导致磁矩扰动。电性能取决于 La3+ 含量和第二相浓度。未掺杂的样品呈现最高的阻抗值，在所有频率范围内呈线性下降。对于掺杂的样品，由于 La3+ 的掺入，电阻率会下降几个数量级，而交流电导率在低频时保持不变，而在高频时呈现色散。介电常数呈现出由 Fe3+ 到 Fe2+ 离子的电子跳跃产生的空间电荷极化机制。虚阻抗和电模块的结果表明了Non-Debye型弛豫和长短程电导率跃迁。键价模型显示，受影响最大的晶体位点是 2b、4f2 和 12k，在这些位置应该发生 Fe3+ 与 Fe2+ 离子的价态交换。