Enhanced Ferromagnetic Ordering in GdBaCo$_{2}$O$_{5.5+\delta}$ Films on SrTiO3 (001) Substrate

TL;DR

This study demonstrates that GdBaCo$_{2}$O$_{5.5+\delta}$ thin films on SrTiO$_{3}$ exhibit significantly enhanced ferromagnetic properties above room temperature due to phase separation and orbital ordering effects.

Contribution

It reveals the mechanism behind enhanced ferromagnetism in epitaxial GdBaCo$_{2}$O$_{5.5+\delta}$ films, highlighting phase separation and orbital order as key factors.

Findings

Remnant magnetization above room temperature in films

Phase separation with $a$-oriented phase responsible for ferromagnetism

Enhanced orbital order of Co$^{3+}$ linked to ferromagnetic enhancement

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.