Magnetization dynamics and Gilbert damping in ultrathin Co48Fe32B20 films with out-of-plane anisotropy

Time resolved magneto-optical Kerr measurements are carried out to study the precessional dynamics of ferromagnetic thin films with out-of-plane anisotropy. A combined analysis of parameters, such as coercive fields, magnetic anisotropy, and Gilbert damping a, is reported. Using a macrospin approximation and the Landau-Lifshitz-Gilbert equation, the effective anisotropy and a are obtained. A large damping varying with the applied field as well as with the thickness of the ferromagnetic layer is reported. Simulations using a distribution in the effective anisotropy allow us to reproduce the field evolution of a. Moreover, its thickness dependence correlates with the spin pumping effect. © 2009 American Institute of Physics.