Second-order spin-wave instability in Mn-Zn2Y planar hexagonal ferrites

The letter describes some measurements of the decline of the main resonance under 2nd-order pumping in an Mn-Zn2Y single-crystal hexagonal ferrite biased in the easy plane. Measurements were carried out with the r.f. field in the easy plane and also with the r.f. field perpendicular to it. The ratio of the two responses in the linear region is e02, which is the ratio of the susceptibilities for the two excitations. The ratio of the two r.f. threshold fields is also approximately e. Here e02 is the uniform-mode ellipticity. For the samples used, the critical r.f. threshold field was 41A/m in the easy plane and the spinwave linewidth was 565A/m.