Multiple resonance peaks of FeCo thin films with NiFe underlayer

Under zero external magnetic fields, single-layer FeCo thin films exhibit no ferromagnetic resonance (FMR) peaks, while multiple FMR peaks were obtained by growing FeCo thin films on NiFe underlayers with various thicknesses up to 50 nm. Comprehensive investigations of the dynamic magnetic properties and origin of the peaks were conducted through measurements of microwave permeability via a shorted microstrip perturbation technique. Through fitted values of saturation magnetization Ms, uniaxial anisotropy H-K(sta), and rotatable anisotropy H-K(rot) extracted from the FMR experiments, it was found that two of the three resonance peaks originate from FeCo, and the third from NiFe. The two magnetic phases of FeCo grains are found to have different values of H(K)(ro)t and explained by the exchange interaction between FeCo and NiFe grains. (C) 2015 AIP Publishing LLC.