Effect of large magnetocrystalline anisotropy on the spin wave linewidth in Zn-Y hexagonal ferrite

The oblique pumping spin wave instability,threshold microwave field amplitude h(crit) was measured as a function of the static field for both in-plane and out-of-plane static fields for a thin disk of Mn substituted Zn-Y (Ba2Zn2Fe12O22) easy plane hexagonal ferrite at 16.7 GHz. Theoretical fits to the in-plane static field data gave a single value of 12.8 Oe for the spin wave linewidth DeltaH(k). The best overall fits were for a critical spin wave mode wave number k close to zero and there was no correlation with the critical mode propagation directions. The fitted DeltaH(k) for the out-of-plane static field geometry was found to increase with the out-of-plane magnetization angle, but showed no: correlation with the critical mode propagation directions. These critical modes had kapproximate to0 as well. The fitted DeltaH(k) increased from the in-plane field value of 12.8 Oe to a value of 21 Oe at the maximum accessible magnetization angle of 70degrees relative to. the disk plane. This increase in spin wave damping with the out-of-plane angle is attributed to spin orbit coupling. (C) 2003 American Institute of Physics.