Doping effect of Sm3+ on magnetic and dielectric properties of Ni-Zn ferrites

Ni-Zn ferrites of nominal composition Ni0.5Zn0.5SmxFe2-xO4 (x=0-0.1) were prepared by a conventional two-steps solid sintering method. The effect of Sm3+ doping on the microstructural, magnetic and dielectric properties of the as-prepared Ni-Zn ferrites were investigated. The main phase of all the samples was ferrite spinel, and the samples doped with Sm3+ ions contained a small amount of a foreign SmFeO3 phase as well. And the doping of Sm3+ resulted in the increase of lattice constant. The grain size, density and densification of the ferrites initially decreased after Sm3+ doping, but then increased with more Sm3+ doped. With increasing substitution level, x, the saturation magnetization of the as-prepared ferrites decreased, while the coercivity increased. The Curie temperature raised initially and decreased later with increasing content of Sm3+ in the samples, reaching a maximum of 274 °C when x=0.025. The initial permeability of the ferrites first decreased and then increased with increasing doping amount of Sm3+ ions. The introduction of Sm3+ ions into Ni-Zn ferrite would lead to the reduced dielectric loss in the frequency range of 1-100 MHz, but the dielectric loss raised when more Sm3+ was added in the frequency range of 100-1000 MHz. When x=0.05, the dielectric loss reached the lowest value.