Magnetostatic Spin Wave in a Very Thin CoFeB Film Grown on an Amorphous FeZr Buffer Layer

The transmission of a magnetostatic spin wave in a very thin CoFeB film (2.3 nm) grown on an amorphous paramagnetic FeZr layer was demonstrated for the first time by using an antenna method with coplanar waveguides. The attenuation length, determined by using the difference in intensities due to a change in the distance between the antennas, was estimated to be 0.7 µm. We discuss why we are able to observe spin-wave propagation in such a thin magnetic layer, taking the low damping constant (α = 0.0027) of the CoFeB films grown on the amorphous FeZr layer and the estimated large group velocity in the CoFeB films into account.