Regensburg 2007 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Spindynamics / Switching III

MA 33.6: Talk

Friday, March 30, 2007, 12:15–12:30, H23

Magnetization dynamics in rare earth doped NiFe films — •Matthias Kiessling¹, Georg Woltersdorf¹, Jan-Ulrich Thiele², Manfred Schabes², and Christian Back¹ — ¹Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany — ²Hitachi Global Storage Technologies, 3403 Yerba Buena Road, San Jose, CA 95135, U.S.A.

The influence of rare earth dopants on the damping parameter and the resulting possibility to control this parameter were investigated. In our experiments NiFe films were doped with Dysprosium, Holmium, Terbium, and Gadolinium. The magnetization dynamics of these rare earth doped films was mainly studied by means of ferromagnetic resonance (FMR) and network-analyzer ferromagnetic resonance.

It is demonstrated that the doping of a NiFe film by a small amount of rare earth elements (Holmium, Terbium and Dysprosium) greatly effects its magnetic relaxation rate. This additional damping is proportional to the doping level. Compared to the pure NiFe film it is possible to increase the damping parameter of the magnetic film by two orders of magnitude. On the other hand Gadolinium as a dopant has no influence on the damping parameter. For small dopant concentrations the in and out-of-plane FMR measurements at various frequencies can be well described by the same damping parameter. This is expected for the Gilbert damping term in the equation of motion. Therefore the increased damping can be attributed to an increased rate of transfer of angular momentum from the spin system to the lattice.