Robust room temperature ferromagnetism in epitaxial CoO thin film

Co vacancy (V-Co) induced robust room temperature ferromagnetism (Ms similar to 60 emu/cm(3) and coercivity similar to 603 Oe) is experimentally realized in rock-salt CoO epitaxial thin film (similar to 110 nm) grown by pulsed laser deposition. Co charge state is found to be higher similar to+3.2 (from Co L-3/L-2 white line ratio) and this is due to the V-Co induced charge transfer from the neighboring Co-3d to O-2p states in order to compensate for the hole formation. O-K and cathodoluminescence spectra corroborate the existence of V-Co and higher charge state. Temperature dependent magnetization and exchange bias experiments confirm the coexistence of ferromagnetic and antiferromagnetic phases. (C) 2013 AIP Publishing LLC.