Microwave losses of polycrystalline ferrites at off-resonance field

The spin wave manifold (spin wave eigenfrequencies) for the grain-surface-layer is obtained from the procession equation, based on the assumption, that in the grain-surface-layer of the polycrystalline ferrite there exists an induced uniaxial anisotropy field H_u which is caused by the impurities depositing nearby the grain boundary and by the stresses due to lattice mismatching. The top and the bottom of the manifold at various applied magnetic fields are illustrated in comparing with the manifold for the inner grain area. It is concluded that the off-resonance effective linewidth ΔH_eff arises from the losses of the spin wave resonance excited on the grain-surface-layers and it is proportional to the volume fraction of grain-surface-layers and sensitive to the grain size and the porosity strongly