Thermal stability of exchange-biased NiFe/FeMn multilayered thin films

Abstract

A systematic study of the effect of ferromagnetic thickness on magnetic and microwave properties of exchange-biased NiFe/FeMn multilayered thin films was carried out with regards to thermal stability. The temperature-dependent microwave characteristics of the films were obtained from the near-field microwave microscopy technique and analysed based on Landau-Lifshitz-Gilbert equation. The complex microwave permeability spectra of the magnetic thin films up to 5 GHz in the temperature range from room temperature to 420 K were measured. It was found that thicker ferromagnetic layers helped to reduce the dependence of the magnetic properties on temperature, leading to better thermal stability. The saturation magnetization MS, dynamic magnetic anisotropy field HKdyn, and ferromagnetic resonance frequency fFMR were found to decrease with temperature, while the effective damping coefficient αeff was increased with temperature. We also investigate the rotational magnetic anisotropy field HKrot with temperature which gives a measure of the rotatable magnetization of the antiferromagnetic layers and its thermal stability.