Field annealing effect on magnetostriction and sensitivity of the ferromagnetic Fe60Co18Ga22/Si(100) film

Highlights: • After field annealing (FA), both macro-stress and magnetostriction of the Fe-18Co-22 Ga film increase greatly. • The tetragonal L1₂ phase shows up after FA treatment. • The occurrence of large stress and magnetostriction is related to the field-induced flip of the tetragonal axis of L1₂ by FA. As-deposit (AD) and field-anneal (FA) Fe₆₀Co₁₈Ga₂₂ films have been made. We found that after FA treatment, both the macro-stress and saturation magnetostriction in the film increase greatly. Also, after FA treatment, the tetragonal L1₂ phase shows up, and coexists within the original two-phase (A2 + D0₃) field. In agreement with the theory, the occurrence of large stress and magnetostriction is related to the magnetic-field-induced flip of the tetragonal axis of the L1₂ phase crystal by FA. As a low-field sensor, FA could enhance the sensitivity of the Fe₆₀Co₁₈Ga₂₂ film element up to 18.9 ppm/Oe.