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 (Fe100-xGax,x = 12.5, 18.4, and 22.0) and Fe-81 Al-19 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 0MsH alpha(z) + K-cubic(alpha(4)(x) + alpha(4)(y) + alpha(4)(z)) + K-uniaxial alpha(2)(z) - lambda T-sat alpha(2)(z), 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.