Magnetic properties of in-plane oriented barium hexaferrite thin films prepared by direct current magnetron sputtering

Abstract

In-plane c-axis oriented Ba-hexaferrite (BaM) thin films were prepared on a-plane (112¯0) sapphire (Al2O3) substrates by DC magnetron sputtering followed by ex-situ annealing. The DC magnetron sputtering was demonstrated to have obvious advantages over the traditionally used RF magnetron sputtering in sputtering rate and operation simplicity. The sputtering power had a remarkable influence on the Ba/Fe ratio, the hematite secondary phase, and the grain morphology of the as-prepared BaM films. Under 80 W of sputtering power, in-plane c-axis highly oriented BaM films were obtained. These films had strong magnetic anisotropy with high hysteresis loop squareness (Mr/Ms of 0.96) along the in-plane easy axis and low Mr/Ms of 0.03 along the in-plane hard axis. X-ray diffraction patterns and pole figures revealed that the oriented BaM films grew via an epitaxy-like growth process with the crystallographic relationship BaM (101¯0)//α-Fe2O3(112¯0)//Al2O3(112¯0).