Resonance Widths in Polycrystalline Nickel-Cobalt Ferrites

The width of the ferromagnetic resonance has been measured at 10 000 Mc/sec in polycrystalline mixed ferrites of the composition ${\mathrm{Co}}_{\alpha }{\mathrm{Ni}}_{1-\alpha }{\mathrm{Fe}}_2{\mathrm{O}}_4$, with $\alpha$ between 0 and 0.04. The minimum line width is found for $\alpha =0.025\mathrm{}$ at 20°C. This, as well as the variation of line width with temperature, can be understood on the basis of known single crystal properties and the following assumptions: (a) line width is a linear function of $\mathrm{}\left|K\right|\mathrm{}$; (b) crystal anisotropy is an additive atomic property.