High-frequency characteristics of metal/native-oxide multilayers

The high-frequency magnetization dynamics of magnetically soft Co_xFe_100-x metal/native-oxide multilayers were studied as a function of alloy composition (10 ≤ x ≤ 50) using a time-domain inductive technique. The data show intrinsic resonance frequencies ranging from 2.1 to 3.7 GHz due to the variation of anisotropy field with x. The frequencies are consistent with a simple ferromagnetic resonance (FMR) response, with the dynamical anisotropy field equal to the static anisotropy field. The large dc permeabilities, ranging from 200 to 1000, are therefore maintained at high frequency. The combination of high permeability, high resonance frequency, low damping, and a tunable anisotropy field, along with a high resistivity, make this system ideally suited to high-frequency applications.