Diffusant relaxation as a source of the divergence from the linear relation of the initial permeability versus grain size in iron deficient YIG and Ni-ferrites

It is shown that, in ferrimagnets containing diffusants, the linear relation between the quasi-static permeability-measured at 1000 Hz usually-and the grain size is no longer valid in the temperature range where the diffusant relaxation frequency is smaller than the permeability measurement frequency.