Fabrication of soft-magnetic FeAlSi thin films with nm-order thickness for the free layer of magnetic tunnel junction based sensors

FeAlSi epitaxial films were fabricated on single crystalline MgO(100) substrates and their structural and magnetic properties were investigated to apply them to the free layer in magnetic tunnel junction (MTJ) based sensors. We found that the film composition must be precisely controlled, and the post-annealing temperature was varied to obtain a D03-ordered structure and soft magnetic property. By adjustment of the film composition and optimizing annealing temperature, we succeeded in obtaining D03-ordered FeAlSi thin films with a small surface roughness and low coercivity. The fabricated FeAlSi film is greatly useful as a free layer material in MTJ based sensor devices.