In-plane c-axis oriented barium hexaferrite films prepared by magnetron sputtering

Abstract

In-plane c-axis oriented M-type barium hexaferrite (BaM) films were grown on a-plane sapphire (112̄0) substrates by radio frequency magnetron sputtering with ex-situ annealing. Oxygen in sputtering atmosphere played a critical role in the c-axis orientation growth of BaM films. With incorporation of 10% O2 during sputtering, in-plane c-axis highly oriented BaM films with high hysteresis loop squareness (Mr/Ms∼0.94) along in-plane easy axis and low Mr/Ms∼0.08 along in-plane hard axis was achieved. In contrast, films sputtered without O2 incorporation showed poor magnetic anisotropy and low hysteresis loop squareness along both directions. The oxygen induced formation of oriented hematite intermediate phase was found, which was supposed to be responsible for the in-plane orientation growth of BaM grains.