Annealing effect of surface magnetic properties in amorphous Co/sub 1-x/Ti/sub x/ thin films

For amorphous Co/sub 1-x/Ti/sub x/ (x=0.13, 0.16, 0.21 at.%) thin films, deposited by the DC magnetron sputtering method, ferromagnetic resonance experiments have been used to investigate the dependence of surface magnetic properties in relation to annealing temperatures (150/spl sim/225/spl deg/C). Spin wave resonance spectra for all annealing temperatures consist of several volume modes and one (or two) surface mode. It is suggested that both surfaces of the film have a perpendicular hard axis to the film plane (negative surface anisotropy). Also, the surface anisotropy K/sub s2/ at the substrate-film interface is varied slowly from -0.11 to -0.25 erg/cm/sup 2/ and the surface anisotropy K/sub s1/ at the film-air interface is varied from 0.16 to -0.53 erg/cm/sup 2/ with increasing annealing temperatures. We conjecture that the variation of surface anisotropy K/sub s1/ is due to the increase of Co concentration resulting from Ti oxidation for low temperature annealing (150-200/spl deg/C) and the diffusion of Co atoms near the film surfaces for high temperature annealing (225-250/spl deg/C).