Magnetic and structural properties of Joule-heated Fe₇₃Al ₅Ga₂P_11-xC₅B₄Si _x amorphous thick ribbons

The effect of Joule heating on the magnetic properties and microstructure was investigated in Fe₇₃Al₅Ga₂P _11-xC₅B₄Si_x (x=1, 3) ribbons with a thickness of about 40μm. It turns out that, in these alloys, the coercive field, the pinning field and the time dependence of the initial permeability decrease with increasing current density applied during a thermal treatment via Joule heating up to the occurrence of crystallization. At the as-cast state, the sample with x=3 exhibits better soft magnetic properties than those of the sample with x=1; however, after an optimum annealing, both alloys present similar magnetic properties. The temperature dependence of the resistivity shows clear two stages crystallization process for the Fe₇₃Al ₅Ga₂P₈C₅B₄Si₃ alloy. The microstructural and magnetic inhomogeneities of the annealed Fe ₇₃Al₅Ga₂P₈C₅B ₄Si₃ alloy with lowest coercivity were investigated by means of a small-angle neutron scattering method. The improvement of the soft magnetic properties caused by Joule heating of materials is due to the internal stress relieve originated during the production of the ribbon and to the enlargement of the domain wall thickness, consequently the reduction of the anisotropy.