Damping constant of Co/Pt multilayer thin-film media

Gilbert's damping constants, alpha, of Co(t(Co))/Pt (1.4 nm) multilayer thin films are investigated by Q-band FMR analysis. alpha is calculated from the resonance width of the FMR spectrum. With decreasing t(Co), the alpha value decreases from 0.034 (t(Co) = 8.7 nm) to 0.023 (t(Co) = 1.8 nm), and then increases to 0.037 (t(Co) = 1.0 nm). The decrease of alpha with t(Co) > 1.8 nm is probably due to the eddy current loss effects. The increase of a with t(Co) < 1.8 nm would be caused by the increase of the distortion between the Co and the Pt layers at the interface. When the magnetic field direction was changed from theta = 90 degrees (parallel to the specimen) to theta = 0 degrees (perpendicular to the specimen), the alpha of all the specimens increased, and a sharp step in alpha was observed around theta = 40, where the alpha has the maximum value. (C) 2008 Elsevier B. V. All rights reserved.