Inductive and magneto-resistive measurements of Gilbert damping in Ni81Fe19 thin films and microstructures

We study time resolved precessional magnetization dynamics of permalloy (Ni81Fe19) thin films by time resolved detection of the anisotropic magneto-resistance (AMR) and by pulsed inductive microwave magnetometry (PIMM). AMR experiments are performed on microstructured permalloy discs of 4 μm diameter. PIMM experiments are performed on unpatterned macroscopic thin films of the same material. The magnetization dynamics observed by AMR can be well described by mainly single domain precession neglecting spin wave excitations. In contrast PIMM experiments on macroscopic samples show evidence of multiple precessional modes which cannot be described by a single Gilbert damping parameter. Consequences of the measurement of the intrinsic Gilbert damping parameter by the two methods are discussed