Ferromagnetic resonance spectra of thick yttrium-iron-garnet films

Due to the finite aspect ratio of the ferrite, the distribution of the internal field in small planar microwave ferrite devices is strongly inhomogeneous. This is a source of additional losses through magnetostatic modes. To study the magnetostatic modes, the thickness dependence of the ferromagnetic resonance spectra was measured for a series of 2 mm square single crystal yttrium-iron-garnet films in the 35 < h < 220 mu m thickness range. The in-plane resonance field H-r increases with thickness by 150 G, while H-r normal to film plane decreases. The uniform mode linewidth, dH(r) is in the 2-20 G range. A large number of magnetostatic wave modes modes is excited, covering the "full spectral width," DH, increasing with thickness from 400 to 960 G. In a ferrite device DH has to be taken into account, giving rise to large losses in spite of the small intrinsic linewidth dH(r) of the material. (C) 2000 American Institute of Physics. [S0021- 8979(00)25808-8].