Ionic order and magnetic properties of double-perovskite GdBaCo₂O_5.5 films on SrTiO₃ substrates

Abstract

Double-perovskite GdBaCo₂O_5.5 epitaxial films were fabricated on SrTiO₃(001) substrates. X-ray diffraction and scanning transmission electron microscopy measurements of a 37 nm thick film confirmed the ionic order of Gd and Ba along the out-of-plane direction. The Gd/Ba order was absent within the region 1 nm from the film/substrate interface owing to the migration of Sr ions from the substrate. Unlike the 37 nm thick film, a thin film with a thickness of 10 nm did not show a distinct antiferromagnetic to ferromagnetic (FM) transition, whereas large magnetization was observed at low temperature. This was proposed to be because the cation-disordered phase near the interface was FM, even at low temperatures.