Magnetic disaccommodation in ferrites with nonmagnetic divalent substitutions

The after-effect processes in magnetite with nonmagnetic divalent substitut ions are studied by means of disaccommodation techniques. We have recorded at room and high temperatures the time evolution of the initial magnetic su sceptibility after sample demagnetization for polycrystalline specimens wit h nominal composition MxFe3-xO4+delta, M being a divalent cation such as Zn 2+, Mg2+, or Ca2+. These ions replace Fe2+ inside the spinel structure and, consequently, affect the original process III in magnetite. We have found that the presence of these ions involves the splitting of process III into similar processes, according to the position of the substituting ions. In a ddition, high-temperature processes are discussed on the basis of vacancy-m ediated diffusion of nonmagnetic metallic ions.