On the instability threshold of cobalt substituted Ni-Al ferrite at high-microwave-power levels

Parallel-pump spin-wave instability in polycrystalline Ni-Al ferrite has been measured at 9.384 GHz. The ground degeneracy of Co2+ ions with concentration between 0.01 and 0.025 ions/f.u. added stoichiometrically, gives minimum losses and high-instability threshold values. Generalized instability theory for oblique pumping is used to reproduce the experimental butterfly curves. Results show a strong dependence of spin-wave linewidth on wave vector and crystalline anisotropy of cobalt