Effect of neutron irradiation on the long-wavelength magnetic excitations in the Zn0.60Ni0.40Fe2O4 ferrite

An energy analysis of small-angle neutron scattering in the Zn_0.60Ni_0.40Fe₂O₄ ferrite nonirradiated and irradiated by fast neutrons has been performed. It has been revealed that the inelastic neutron scattering in the initial ferrite below T _C is due to not only the intradomain spin waves but also the significant contribution of the intraboundary long-wavelength magnetic excitations (w) and those localized near the domain boundaries (nw). The number of these magnetic excitations in the irradiated sample is significantly smaller. The elevated density of states of the w and nw magnetic excitations is assumed to be related to the competition between the intersublattice and intrasublattice exchange interactions, which is significantly weakened in the irradiated ferrite, where the corresponding exchange integrals are related by the inequality J _AB ? J _BB .