High permeability and stress insensitivity of MgCuZn–NiCuZn ferrite composites for microinductor applications

Ferrite composites with ferrimagnetic phases (X) Ni_0.35Cu_0.05Zn_0.6Fe₂O₄ + (1 − X) Mg_0.25Cu_0.25Zn_0.5Fe₂O₄ in which X varies from 0.0 to 1.0 were prepared by conventional ceramic double sintering process. The formation of single phase spinel structure was confirmed by X-ray diffraction. Initial permeability measurements on the pure components and their composites were carried out in the temperature range 30–250 °C. These studies show that the composites possess high initial permeability compared to the pure components. The ferrite composite with X = 0.5 showed a high initial permeability of μ_i = 9,619. This is explained with the help of excess properties of the solid solution. Since, the equimolar composition showed high initial permeability, (μ_i) stress sensitivity studies in the pure components and their equimolar composition were explored and these studies revealed that the equimolar composition exhibits a stress insensitive property. In view of the high permeability of these composites and stress insensitivity, equimolar composition of these ferrites can be exploited as core material for microinductor applications.