Effect of MnTi and MnSn substitutions on the magnetic properties of Ni–Zn ferrite

Polycrystalline ferrites with the chemical composition Ni0.6Zn0.4A2xFe2−2xO4, where A=(MnxTix)/(MnxSnx), x=0.0, 0.1, 0.2, 0.3 and 0.4, were prepared by ceramic method. They were characterized by X-ray and SEM. The lattice constant increases with x in both the series. This is related to the ionic radii of the substituents. The saturation magnetisation (Ms) and the Curie temperature (Tc) decrease with x. The magnetic behaviour is explained on the basis of Neels model and the canting is due to the presence of Mn at the A site and of Ti/Sn at B site. The initial permeability (μi) increases with x, upto x≤0.2 for Ti and then decreases with further increase in x, whereas it decreases continuously with x for Sn. The main contribution to permeability is due to the domain wall motion. The variation of permeability with frequency shows relaxation. The relaxation frequency increases with x in both the series. However, the relaxation frequency is higher in case of Sn series. The variation in permeability is mainly accounted for to be due to microstructural changes. The thermal variation of permeability is related to the stability of Fe–Ti and Fe–Sn pairs.