Structural and electromagnetic properties of Ni0.5Zn0.5HoxFe2-xO4 ferrites

Ni-Zn ferrites with a nominal composition of Ni_0.5Zn_0.5Ho_xFe_2-xO₄ (x = 0–0.06) were prepared by conventional solid state reaction through using analytical-grade metal oxides powders as raw materials. The phase composition, microstructure, magnetic properties and dielectric performance of the as-prepared samples were investigated. The doped Ho³⁺ ions could enter into the crystal lattice of the resultant spinel ferrites, causing the expansion of the unit cell, reaching a saturated state when x = 0.015; and the additional Ho³⁺ ions would form a foreign HoFeO₃ phase at the grain boundary. The grain size and densification of the samples initially decreased after a small amount of Ho³⁺ ions was doped, but then increased with more Ho³⁺ ions added. The saturation magnetization decreased gradually with increasing substitution level of Ho³⁺ ions. The Curie temperature and coercivity raised initially and declined later with increasing content of Ho³⁺ ions in the samples, reaching their maximums of 305 °C with x = 0.015 and 2.99 Oe with x = 0.03, respectively. The variation of complex permeability versus Ho³⁺ ions substitution level presented an opposite trend to that of coercivity. The dielectric loss increased slightly after the introduction of a small amount of Ho³⁺ ions, but reduced significantly with more Ho³⁺ ions doped.