Induced Magnetic Anisotropy in Stress-Annealed Galfenol Alloys

Values of the uniaxial anisotropy, cubic anisotropy, saturation magnetic induction, and saturation magnetostriction were obtained from measurements of the magnetization and magnetostriction of stress-annealed Galfenol (Fe_100-xGa_x,x=12.5,18.4, and 22.0)and Fe₈₁Al₁₉ as a function of compressive stresses <100 MPa. The values were derived from fitting magnetization and magnetostriction curves to the energy expression E_i=-mu ₀M_sHalpha_z+K_cubic(alpha _x ⁴+alpha_y ⁴+alpha_z ⁴)+K_u n_iaxialalpha_z ²-lambda_satTalpha_z ², where M_s,lambda_sat and the K´s are fit parameters. The alpha_i´s are the direction cosines of the magnetization direction with respect to the field and stress direction (z).H is the magnetic field and T is the measurement stress (compressive T<0). Data are fit with high precision by only the above four constants plus a smoothing constant. Importantly, K_uniaxial enables a prediction of the maximum usable tensile stress