Effect of magnetocrystalline anisotropy on the magnetic spectra of Mg–Fe ferrites

Results of new experiments on magnesium-iron ferrites at 26° C and −196° C are presented. These include measurements of the first-order magnetocrystalline anisotropy constant K of monocrystals, and of the magnetic spectrum (the frequency dependence of the complex initial permeability) of polycrystals. If a newly observed inversion dependence of K is neglected, the values of K at room temperature are represented by K = − 85000x − 25000 ergs/cm3 where x is defined by the formula (MgO)1−x(FeO)xFe2O3. Frequencies between zero and 104 Mc/s were used for the magnetic spectra, and two or three pronounced dispersions were observed in each ferrite. Some earlier investigations concerned with the magnetic spectra of sintered ferrites possessing two broad dispersion regions are reviewed. It is concluded from the present and earlier investigations that the radio-frequency dispersion region and the static initial permeability are primarily due to domain wall displacements, and that the microwave dispersion region is primarily due to domain rotations that occur in an effective field caused by magnetocrystalline anisotropy as well as by static and dynamic magnetic interactions.