ANGLE DEPENDENCE OF THE FERROMAGNETIC-RESONANCE LINEWIDTH IN EASY-AXIS AND EASY-PLANE SINGLE-CRYSTAL HEXAGONAL FERRITE DISKS

Ferromagnetic resonance measurements were made asa function of the sta tic external field angle for c-plane disks of single crystal flux grow n manganese substituted barium M-type (Ba-M) and zinc Y-type (Zn-Y) he xagonal ferrites at 50 and 8.8 GHz, respectively. A shorted waveguide technique was used, Analysis of the FMR field versus angle results con firmed the operational assumption of a uniform mode response, For the easy-axis Ba-M disk, the linewidth was 69 Oe when the external field a nd magnetization vectors were perpendicular to the disk. The Linewidth increased to a maximum measured value of 472 Oe when the magnetizatio n was directed 45.4 degrees from the sample normal. For the easy-plane Zn-Y disk, the linewidth had a minimum value of 18 Oe when the field and magnetization vectors were in-plane, The maximum linewidth was 391 Oe when the magnetization was directed 25.2 degrees from the disk nor mal. The linewidths were larger than predicted for reasonable values o f the Landau-Lifshitz damping and showed angle dependences which indic ated nonintrinsic contributions to the loss, A modified two magnon sca ttering calculation based on the model of Sparks, Loudon, and Kittel w as used to investigate these Linewidth differences. The calculation in cluded anisotropy modifications to the spin wave band for each materia l. The angle dependences of the excess linewidths show qualitative agr eement with the two magnon predictions, with inhomogeneity sizes on th e order of 1 and 0.25 mu m and volume fractions of 0.01 and 0.005 for the Ba-M and Zn-Y disks, respectively. (C) 1997 American Institute of Physics.