Orientation Dependence of Spin-Wave Spectra in Single-Crystal YIG Films

Abstract

Spin-wave resonance in epitaxial films of yttrium iron garnet (YIG) has been studied as a function of the orientation of the static field H relative to the film plane and the crystallographic axes. The positions, intensities, and linewidths of the main branch and the higher branches have been measured in (100) and (110) disks with thicknesses from 0.37 to 1.15 μ. Higher branches which are spaced more than ∼100 Oe from the main branch in perpendicular resonance (H⊥film, θ = 90°) disappear between θ = 90° and θ = 0°, while those which are closer are present over the entire range of θ. In a 0.37-μ, (100) film the first higher branch disappears at θ = 49°. It reappears one degree on either side of this critical angle and is spaced ∼50 Oe from the main line at these points. The linewidth of the first higher branch reaches a maximum of 7.1 Oe near θ = 49° and decreases to values of 2.0 and 2.4 Oe at θ = 90° and 0°, respectively. The main branch linewidth increases monotonically from 1.8 to 7.1 Oe between θ = 90° and θ = 0°. Anisotropy of the spin-wave spectrum is observed in parallel resonance (H ∥ film, θ = 0°) of both (100) and (110) films. In a 0.9-μ, (110) sample the spacing between the first two branches is almost identical in the [110] and [111] directions, but is ∼50% less in the [100].