GMI Effect in Annealed $Fe_{40}Ni_{38}Mo_{4}B_{18}$ Microwires

Amorphous glass-coated microwires are ideal material for miniaturized applications for sensing the temperature, stress and magnetic field. One of the key parameters for future applications is their time and thermal stability. It has been shown that stability can be improved by using nanocrystalline materials that combine good soft magnetic properties of amorphous matrix with high structural stability of crystalline grains. Such nanocrystalline materials are usually obtained by annealing of amorphous precursor. In the given contribution, the influence of dc current annealing on the domain structure and GMI effect in amorphous and nanocrystalline $Fe_{40}Ni_{38}Mo_{4}B_{18}$ magnetic microwire has been studied. The annealing induces additional circular magnetic anisotropy, stress relief and structure homogenization. However, the increase of magnetostriction results in the decrease of GMI. Annealing at optimum crystallisation temperature results in an increase of the relative permeability due to the formation of the nanosized grains. Consequently, GMI amplitude is comparable to that of as-cast state.