The Effect of Externally Applied Uniaxial Compressive Stress on the Magnetic Properties of MnZn-Ferrites

Abstract

The present work deals with the effect of uniaxial compressive stress on the magnetic properties of MnZn-ferrite materials with permeability levels between 2000–12000. The investigation included the effects of several process operational or material structural parameters such as time and periodical stress application and removal, sintering partial pressure of oxygen, final density and grain size on the stress sensitivity of the polycrystalline material. It was found that stress sensitivity increases with permeability, while the high permeability grades show a permanent decrease of the permeability level under prolonged application of the applied stress. Regarding the power MnZn ferrite materials, a reduction of the secondary permeability maximum temperature by ~0.5°C MPa⁻¹ and a subsequent reduction in magnetic flux density by ~1.4 mT MPa⁻¹ upon the exertion of uniaxial compressive stress was measured. In addition, it was observed that there is an optimal partial pressure of oxygen during sintering, under which the stress sensitivity of the material becomes minimum. A mechanism of anisotropy field variations induced in the material in combination with the defect structure of the material and its dependency on the partial pressure of oxygen has been proposed.