Magnetic properties of Ni ferrites substituted by divalent Zn, Cu and Co ions

Abstract

Substituted Ni ferrite samples with chemical composition Nil_x_ Y _ Z ZnxCuyCozFe204, where x = 0.4, 0.5 and 0.6, y = 0.1, z = 0.01 and 0.02 were prepared by classical ceramic technology at the temperature of 1200°C. The influence of divalent Zn, Cu and Co ions substitution on the magnetic properties of spinel Ni ferrites was studied. The magnetic properties, such as the Curie temperature, coercive field, remanent magnetic flux density, hysteresis loop area as well as the amplitude and initial permeability were investigated by means of thermo-magnetic analysis and magnetisation curves measurements at low frequencies. 1. INTRODUCTION NiZnCuCo ferrites belong to ferrimagnetic ceramic materials with spinel, i.e. cubic structure of dominant ionic nature. The elementary cell consists of 8 ferrite molecules containing in total 32 0-anions and 24 metallic cations where the metallic cations occupy the tetrahedral (A) or the octahedral (B) sublattice. The simplest 2-3 spinels comprise of divalent and trivalent cations. The spinel with normal cation distribution is characterised by divalent cations occupying tetrahedral A sites and trivalent cations occupying octahedral B-sites. When the trivalent cations occupy tetrahedral A-sites and the divalent and remaining trivalent cations are presented in octahedral B sites we speak of inverse cation distribution. This alignment is characterised for nickel ferrite NiFe z 04 with cation distribution (Fe3+)A[Ni z +Fe3+]BOl-. The substitution of Ni2+ ions by Zn2+ ions having a strong preference to occupy A-sites leads to mixed spinel structure whose cation distributions are normal with respect to Zn and inverse from the viewpoint of Ni spinel structure [1-3]. In case of Zn, Cu and Co substituted Ni ferrite with chemical composition Nil_x_y_zZnxCuyCozFe 2 04 IOns occupy A-and B-sites in agreement with alignmentThese materials appear to be perspective for high-frequency applications -as such they are extensively studied, see e.g. [3].