Effect of interface on epitaxy and magnetism in h-RFeO₃/Fe₃O₄/Al₂O₃ films (R  =  Lu, Yb)

We have carried out the growth of h-RFeO₃ (0 0 1) (R  =  Lu, Yb) thin films on Fe₃O₄ (1 1 1)/Al₂O₃ (0 0 1) substrates, and studied the effect of the h-RFeO₃ (0 0 1)/Fe₃O₄ (1 1 1) interfaces on the epitaxy and magnetism. The observed epitaxial relations between h-RFeO₃ and Fe₃O₄ indicate an unusual matching of Fe sub-lattices rather than a matching of O sub-lattices. The out-of-plane direction was found to be the easy magnetic axis for h-YbFeO₃ (0 0 1) but the hard axis for Fe₃O₄ (1 1 1) in the h-YbFeO₃ (0 0 1)/Fe₃O₄ (1 1 1)/Al₂O₃ (0 0 1) films, suggesting a perpendicular magnetic alignment at the h-YbFeO₃ (0 0 1)/Fe₃O₄ (1 1 1) interface. These results indicate that Fe₃O₄ (1 1 1)/Al₂O₃ (0 0 1) could be a promising substrate for epitaxial growth of h-RFeO₃ films of well-defined interface and for exploiting their spintronic properties.