Enhanced Ferromagnetic Ordering in GdBaCo${}_2$O${}_{5.5+\delta }$ Films on SrTiO3 (001) Substrate

Abstract

The authors investigated the structure and properties of GdBaCo${}_2$O${}_{5.5+\delta }$ thin films epitaxially grown on SrTiO${}_3$ (001) single crystal substrates. The thin films were found to have a notable remnant magnetization above room temperature, which is much higher than that observed in bulk material. Transmission electron microscopy and x-ray diffraction patterns reveal that phase separation occurs in these films, and the phase responsible for the enhanced ferromagnetic order is $a$-oriented. The enhanced ferromagnetic order is attributed to the enhanced orbital order of Co${}^{3+}$ in CoO${}_5$ pyramids, and the disappearance of ferromagnetic to antiferromagnetic transition is explained the stabilization of higher spin state of Co${}^{3+}$ in CoO${}_6$ octahedra.

4 pages, 4 figures