Spin wave excitations in exchange spring Co/CoPt thin film bilayers

We report Brillouin light scattering data taken from an exchange spring bilayer, Co/CoPt. The results are analysed using a semi-classical model in the long wavelength limit, and we demonstrate how a measure of an anomalous volume anisotropy, which we tentatively ascribe to a magnetoelastic effect, can be obtained from frequency versus field measurements in this system.