Stress insensitive NiCuZn ferrite compositions for microinductor applications

Two series of stoichiometric and iron deficient NiCuZn ferrites were prepared by the conventional ceramic method. The formation of single phase was confirmed by X-ray diffraction in pure ferrites and a second phase was noticed in SiO2 added ferrite samples. Initial permeability measurements on these samples were carried out in the temperature range of 30–300 °C. The effect of external applied stress on the open magnetic circuit type coil with these ferrite cores was studied by applying uniaxial compressive stress parallel to the magnetizing direction and the change in the inductance was measured. These studies show that stress sensitivity is more in stoichiometric ferrite samples than in iron deficient ferrite samples. In order to make them stress insensitive various amounts of SiO2 were added and the stress insensitivity was examined. SiO2 addition was found to be effective in reducing the stress sensitivity. This was confirmed by elastic behaviour studies at room temperature on these ferrite samples by employing composite oscillator technique. These ferrite compositions have been developed for their use as core materials for microinductor applications.