We experimentally investigated the crystallographic anisotropy of the intrinsic Gilbert damping constant in single crystalline Fe(001) film deposited on MgO(001) substrate. The frequency-domain ferromagnetic resonance (FMR) spectrum was measured at given external magnetic fields via a vector network analyzer. From the field-domain FMR linewidth obtained as a function of resonant frequency, the intrinsic Gilbert damping constants along the crystallographic axes in the (001) plane were successfully obtained by evaluating the extrinsic influence of two magnon scattering and inhomogeneity. A four-fold crystalline anisotropy of the intrinsic Gilbert damping constant, similar to the magnetic crystalline anisotropy in the (001) plane, was clearly observed. Furthermore, we found that the intrinsic Gilbert damping constant along the easy axis was smaller than that along the hard axis.

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  A method to measure wideband permeability was developed for 5-mm-square magnetic thin film from 0.1 to 10 GHz by using a shielded short-circuited microstrip line as the test fixture. The S₁₁ parameters of the test fixture were measured with a vector network analyzer (VNA). The permeability was derived, based on the lumped element approximation, by comparing S_11s with S_11os which corresponded to without and with a strong magnetic field parallel to the microwave magnetic field caused by the microstrip line. In this case, the influence of substrate on which the thin film prepared could not be neglected due to the small gap between the microstrip line and the substrate. We introduced a method to derive an effective permittivity ε_e caused by the substrate by comparing S_11o of blank fixture with S_11os of fixture with sample under a strong static magnetic field. We also propose a method of determining whether the lumped element approximation is valid or not.

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