Dissipation of spin angular momentum in magnetic switching.

Applying one ultrashort magnetic field pulse, we observe up to 10 precessional switches of the magnetization direction in single crystalline Fe films of 10 and 15 atomic layers. We find that the rate at which angular momentum is dissipated in uniform large angle spin precession increases with time and film thickness, surpassing the intrinsic ferromagnetic resonance spin lattice relaxation of Fe by nearly an order of magnitude.

Surface roughness induced extrinsic damping in thin magnetic films.

The ferromagnetic relaxation caused by the surface roughness induced 2-magnon scattering is investigated. Approximate analytical solution predicts nonexponential decay of the uniform precession excitations of the form exp[-|t/tau3/2|3/2]. This behavior as well as the dependence of the decay time tau(3/2) on roughness parameters are confirmed by micromagnetic simulations.

Intrinsic nonlinear ferromagnetic relaxation in thin metallic films.

We propose an intrinsic mechanism for ferromagnetic relaxation in thin films that can dominate competing linear mechanisms even for rapidly relaxing metals. In particular, we use an analytic theory of four-magnon scattering to demonstrate rapid decay for technologically important systems involving high moment materials subject to large rotations. A micromagnetic simulation is used to verify the results.