The effect of thermal treatment, composition and substrate on the texture and magnetic properties of FeCo thin films

Magnetostrictive FeCo films (thickness 300 nm) have been produced by RF magnetron sputter deposition. The effects of the substrate, composition and thermal treatment on the structural and magnetic properties of the films have been determined. Structural analysis was performed using transmission electron microscopy and x-ray diffraction. The magnetic properties, including magnetostriction, were determined by the magneto-optical Kerr effect, magnetic force microscopy and strain-modulated ferromagnetic resonance. It is found that the magnetic softness of the films is critically dependent on the texture and strain state of the film. With suitable choices of substrate, composition and thermal treatment, these parameters can be controlled, producing magnetically soft films while maintaining a high magnetostriction The differential response of the magnetic anisotropy to strain in these films is comparable to the best values achieved by more involved manufacturing processes, such as multilayering, showing excellent potential for their use in magnetic sensors and actuators.