Tailoring of magnetic properties of glass-coated microwires by current annealing

The effect of dc current annealing (CA) (with duration up to 50 min for current density, j, up to 470 A/mm2), with or without dc axial magnetic field, on the magnetic properties of Co56.5Fe6.5Ni10B16Si11, Fe70B15Si10C5 and Co68Mn7Si10B15 glass-coated microwires has been studied. Such thermal treatments modify the magnetic parameters, such as coercivity. Such a phenomenology can be interpreted by considering the noticeable longitudinal magnetic anisotropy induced by the combined effects of the magnetic field and internal stresses arising from the coating during the thermal treatment. Magnetic hardening (with a coercivity of around 5000 A/m) correlated with the crystallization process has been observed in Co-rich microwires after CA at j=470 A/mm2. An Fe-rich composition has a hysteresis loop typical for a two-phase structure under current annealing at j=470 A/mm2.