Effect of pressure on soft magnetic materials

After a review of previous work, the authors show their results obtained in the study of the effect of pressure on the magnetization mechanisms of polycrystalline soft ferrites up to 1.5 kbar and in a temperature range from 263°K to 573°K. Three kinds of pressures were applied : hydrostatic pressure, lateral pressure inducing stresses along the director circles of toroids and pressure perpendicular to the plane surfaces of toroids. All the results concerning reversible and irreversible magnetization mechanisms under hydrostatic pressure are explained from an unique idea: the change in the topography of domain walls in the grains due to random stresses from the hydrostatic pressure because of compressibility anisotropy. That was confirmed by the effect of directional stresses and by a pressure induced hysteresis. The origin of the compressibility anisotropy was found in the closed porosity.