Field annealing effect on amorphous (FexCo1-x)85Nb15 alloys

The magnetic anisotropy induced by magnetic field annealing was examined for amorphous (Fe_xCo_1-x)₈₅Nb₁₅ alloys produced by a sputtering technique. An appreciably large uniaxial anisotropy was observed even at x = 0. The anisotropy constant (K_u) obtained was 2.3x10³ erg/cm³ at x=0, and it increased with x, showing a maximum of about 5.4x10³ erg/cm³ near x = 0.2. This compositional change in K_u was explained in terms of the directional ordering of magnetic Fe-Co atom pairs under the negative nonmagnetic interaction energy leading to a precipitation.