Study on the Damping Constants of Ni-Fe Thin Films using Different CPW-FMR Measurements

This paper reports the study on the damping constant α of Ni-Fe films using both one and two port type coplanar waveguide-ferromagnetic resonance (CPW-FMR) measurements, and compared these results with a conventional FMR (cavity-type FMR) measurement. In each CPW-FMR measurement, for the films thicker than 10 nm, each α becomes constant in the range of 0.012-0.014. On the other hand, for the film thickness less than 10 nm, α increases from 0.014 to 0.017 as the film thickness decreases, which may be attributed to structural inhomogeneity in the films. These results are in good agreement with those obtained from the cavity-type FMR measurement. On the basis of these results, it is pointed out that α of Ni-Fe films can be evaluated accurately by either of the CPW-FMR measurements. These results also mean that the one port type CPW-FMR measurement is more effective than the two port type CPW-FMR measurement for characterization of Ni-Fe films because the former method is simple and a stronger high frequency magnetic field can be generated.