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

• An interfacial layer of 20-nmthick BaM is introduced between the film and substrate.
• The interfacial layers deposited at various substrate temperatures (Ts) were studied.
• The texture and perpendicular c-axis orientation are greatly improved when Ts = 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 (Ts) on the surface morphologies, crystallographic and magnetic properties of the films were investigated. Experimental results indicated that the interfacial layer deposited at Ts 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 (Δθc) as small as 0.28°. However, in the BaM thin films with an interfacial layer deposited at Ts 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.