Temperature dependence of the parallel-pump spin-wave instability in porous yttrium iron garnet

Abstract

The parallel-pump spin-wave instability threshold has been measured at 8.88 GHz in porous polycrystalline YIG at temperatures ranging from 88 K to 368 K. Sample porosities ranged from <0.5% to 16.3%. The shapes of the low-temperature butterfly curves suggest that the previously inferred inverse wavenumber dependence of the spin-wave linewidth ΔHk may not be valid in porous YIG. The temperature dependences of the ΔHk are incongruous with those predicted by the various transit-time models of spin-wave relaxation. They are also markedly different from those reported for the off-resonance effective linewidth ΔHeff, which suggests that different mechanisms determine ΔHeff and ΔHk.