Employment of Co underlayer and oblique deposition to obtain high resonance frequency and excellent thermal stability in FeCo thin films

•We prepared FeCo thin films with Co underlayer using oblique deposition technique.•The thermal stability of microwave properties of the bi-layer films was studied.•The permeabilities were got using shorted micro-strip transmission-line perturbation.•The films with high resonance frequency tunable up to 6.2 GHz were obtained.•The films with thermal stability within 1% at temperature up to 420 K were obtained.

We propose a novel approach using Co underlayer to grow FeCo thin films by sputtering oblique deposition technique to achieve desirable performance for high frequency applications working in an environment where in the temperature may fluctuate. In particular, the films show a very high resonance frequency tunable up to 6.2 GHz with the permeability of 391 and an excellent thermal stability with the variation less than 1% in the temperature range from 300 K to 420 K.