Tailoring Magnetization Dynamics at the Nanoscale

Controlling spin relaxation is essential for spintronic and spin torque applications. Manipulating spin relaxation allows the adjustment of magnetization reversal speed at microwave frequencies. Moreover, the critical current in spin torque devices can be reduced and tuned. In the experiment it is possible to distinguish between the intrinsic and extrinsic relaxation channels. The latter can be tailored with respect to the intensity and anisotropic behaviour. In particular, methods for inducing elementary relaxation channels of uniaxial symmetry and their impact on the magnetization dynamics are discussed in this presentation. Fe-based thin films have been studied by means of the ferromagnetic resonance technique, by which the intrinsic and extrinsic relaxation processes can be disentangled. While the former are rather isotropic and can be adjusted via spin-orbit interaction, the latter can be modified in an advanced way. It is shown, how crystalline defects, inhomogeneities of chemical composition, and interface modifications can induce the 2-magnon scattering. Control and systematic manipulation of these parameters allow tailoring the overall spin relaxation in a desired manner with respect to the direction of magnetization and precessional frequency.