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MA: Fachverband Magnetismus

MA 15: Magnetic measurement methods

MA 15.6: Talk

Tuesday, March 17, 2015, 10:45–11:00, H 1012

Temperature dependence of the ferromagnetic resonance in magnetic films — •Kristof M. Lebecki — Nanotechnology Centre, VSB-TU Ostrava, Czech Republic

Ferromagnetic resonance (FMR) is an important experimental tool. The well-known FMR line width equation can be extended e.g. by including the Bloch-Bloembergen relaxation. Thus, two-magnon scattering is included. We present here a different approach. Recently proposed Landau-Lifshitz-Bloch approach (LLB) is namely an extension of the Landau-Lifshitz-Gilbert equation (LLG). Contrary to LLG, LLB is valid in the whole temperature range, up to the Curie temperature. We have theoretically analyzed the LLB equation and derived the resonance conditions for the case of a thin film and an in-plane DC field. As a result we got a complex equation for the resonance field that must be solved numerically. However, we propose a handy approximation working well in the whole temperature range. Basing on the resonance field, the FMR line width can be calculated analytically. We show the results of our calculations considering a permalloy film. The resonance field grows remarkably with the temperature. The line width dependence on the microwave frequency is no more linear, a fact that has been observed experimentally in the past. Also, the line width grows with the temperature.