Tensor components of the magnetization in a twisted Fe-rich amorphous wire

Four components of the susceptibility tensor of a high magnetostrictive amorphous Fe77.5Si7.5B15 wire are investigated by means of ac hysteresis loop measurements. The samples have been carefully annealed in order to eliminate the internal stresses produced during the quenching. When tensile stress and/or torsion are applied bistable magnetic behavior with a large Barkhausen jump is observed. The effect of applied torque on the longitudinal and circular components of remanence magnetization and on the longitudinal and circular coercive fields is studied for different constant values of tensile stress. With increasing torque the axial and circular components of remanence decrease and increase, respectively, approaching the limit value of 0.71 Ms. The axial coercive fields for the axial and radial magnetization components coincide. They are nearly constant at low torsion and above same threshold value, depending on applied stress, follow approximately a square-root dependence on applied torque. When tensile stress is applied the circular coercive fields show a well pronounced minimum at the same threshold torque. The experimental results are interpreted by taking into account the axial and helical components of magnetic anisotropy induced by magnetoelastic coupling.