Magnetic Anisotropy And Spin Wave Relaxation In Cofe/Ptmn/Cofe Trilayer Films

We investigated the magnetic anisotropic properties and the spin wave relaxation in trilayer films of CoFe/PtMn/CoFe grown on the seed layer Ru or NiFeCr with CoFe compositions being Co-16 at. % Fe. The measurements were taken in samples with the ferromagnetic layers of CoFe varying from 10 to 500 angstrom by the ferromagnetic resonance (FMR) technique. The magnetic anisotropic parameters were investigated by rotating the field aligned axis with respect to the spectral field in the configurations of both in plane and out of plane. We determine the effective in-plane anisotropy field of similar to 0.005 T, the uniaxial out-of-plane anisotropy of similar to-0.3 T, and the exchange stiffness D of similar to 512 meV angstrom(2). Moreover, spin wave damping was estimated by analyzing the FMR linewidth and line shape as a function of the angle between the external field and easy axis and as a function of the thickness of the CoFe layers. We identify an extrinsic contribution of the damping parameter dominated by two-magnon scattering in addition to the intrinsic Gilbert term with a damping parameter, alpha = 0.012. Further, we reveal that a significant linewidth broadening could also be caused by the overlap of the surface and the uniform spin wave excitations. The FMR lines show a strong dependence of the surface anisotropy contribution of free energy in trilayer films. c 2009 American Institute of Physics. [DOI: 10.1063/1.3093927]