  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.
