Microstructure and magnetic properties of hexagonal barium ferrite thin films with various underlayers

Abstract

BaM (barium ferrite) thin films and underlayers (Fe, Cr, Al2O3, Fe2O3, ZnFe2O4, TiO2) were prepared by rf/dc magnetron sputtering on (100) oriented bare Si substrates. The effects of the underlayer on grain orientation, magnetic properties, and microtexture of BaM film were studied. All the BaM films, except BaM/Fe/Si film, attained nearly the same perpendicular and in-plane coercivities. The BaM/TiO2/Si exhibits the highest coercivity. However, regardless of the underlayer, BaM grains are randomly oriented. By adopting ZnFe2O4 as an underlayer, the interdiffusion of Si from substrate was prohibited to some degree. Elongated grains from the extinction of small platelet grains were grown with an increase in the BaM film thickness of BaM/Si. The microstructure of BaM in BaM/TiO2/Si was strongly dependent on both the microstructure of TiO2 underlayer and the total sputtering gas pressure.