The Fe100-xCox alloy thin films with dilute Co concentrations (x < 11) were prepared on GaAs(001) substrates by RF magnetron sputtering, and their dynamic magnetic properties were investigated by ferromagnetic resonance spectroscopy operating at Q-band (35 GHz). The magnetization curves measured by VSM show clear dependence on the in-plane field directions, indicating bcc Fe100-xCox films were epitaxially grown on the substrates. The ferromagnetic resonance linewidths include both intrinsic and extrinsic magnetic damping. The origins of the latter were examined to extract the intrinsic damping. The estimated upper bounds of the Gilbert damping constants, caused by the intrinsic damping, depend on the Co compositions; the damping is accelerated as Co concentration increases in the region with x < 11.
2013 The Magnetics Society of Japan