Properties of Ba-hexaferrite thin films with an interfacial layer deposited at various substrate temperatures

Abstract

• An interfacial layer of 20-nmthick BaM is introduced between the film and substrate. • The interfacial layers deposited at various substrate temperatures ( T s ) were studied. • The texture and perpendicular c -axis orientation are greatly improved when T s = 300 °C. M-type Ba-hexaferrite (BaM) thin films with a 20 nm thick BaM interfacial layer were deposited on (0 0 1) sapphire substrates by RF magnetron sputtering. Effects of the interfacial layers deposited at different substrate temperatures ( T s ) on the surface morphologies, crystallographic and magnetic properties of the films were investigated. Experimental results indicated that the interfacial layer deposited at T s of 300 °C greatly enhanced the growth of c -axis perpendicularly oriented columnar-type grains and improved the crystallinity of hexagonal BaM phase. BaM thin film prepared on this interfacial layer exhibited an excellent perpendicular c -axis orientation with c -axis dispersion angle (Δ θ c ) as small as 0.28°. However, in the BaM thin films with an interfacial layer deposited at T s either lower or higher than 300 °C, acicular-type grains keeping their c -axis in-plane and/or randomly oriented were grown, thus the crystallographic characteristics and perpendicular c -axis orientations deteriorated.