Effect of preparation condition on the soft magnetic properties of FeCuNbSiB thin films

Amorphous films of finemet composition (Fe73.9Nb3.1Cu0.9Si13.2B8.9) have been prepared using ion-beam sputtering of a target made out of amorphous ribbons of same composition. Two different energies of the Ar-ion, namely 500 and 1000 eV have been used for sputtering. The two films exhibit significant difference in their thermal stability as well as magnetic properties. Both the films in the as-prepared form possess uniaxial magnetic anisotropy in the film plane, which persist up to the first step of crystallisation. Variations in coercivity with the degree of nanocrystallisation can be understood in terms of the random anisotropy model proposed for nanocrystalline alloys, taking into account the finite thickness of the film as compared to the magnetic exchange length.