Parallel Pumping in Hexagonal Ferrites with the Dc Field Off the Easy Plane

This paper gives the theory of spinwave instability under parallel pumping in hexagonal Zn₂Y ferrites with planar anisotropy in the case of a sphere. The configuration considered in this paper is the one in which the dc field makes an angle β with the easy plane and the resultant magnetization lies at an angle α to it. To obtain parallel pumping with this arrangement it is necessfly to align the RF field along the magnetization. This leads to a new spinwave spectrometer which allows the dependence of the spinwave linewidth upon the angle α which the unstable spinwave makes with the c axis of the crystal to be determined. The experimental results obtained on two Mn-Zn₂Y single-crystal ferrite spheres show that the spinwave linewidth increases with the angle α.