Modification of crystal anisotropy and enhancement of magnetic moment of Co-doped SnO thin films annealed under magnetic field.

Co-doped SnO thin films were grown by sputtering technique on SiO/Si(001) substrates at room temperature, and then, thermal treatments with and without an applied magnetic field (H) were performed in vacuum at 600°C for 20 min. H was applied parallel and perpendicular to the substrate surface. Magnetic M(H) measurements reveal the coexistence of a strong antiferromagnetic (AFM) signal and a ferromagnetic (FM) component. The AFM component has a Néel temperature higher than room temperature, the spin axis lies parallel to the substrate surface, and the highest magnetic moment m =7 μ/Co at. is obtained when H is applied parallel to the substrate surface. Our results show an enhancement of FM moment per Co from 0.06 to 0.42 μ/Co at. for the sample on which H was applied perpendicular to the surface. The FM order is attributed to the coupling of Co ions through electrons trapped at the site of oxygen vacancies, as described by the bound magnetic polaron model. Our results suggest that FM order is aligned along [101] direction of Co-doped SnO nanocrystals, which is proposed to be the easy magnetization axis. [ABSTRACT FROM AUTHOR]