Evidence of defect-mediated magnetic coupling on hydrogenated Co-doped ZnO

Hydrogenated bulk Zn1−xCoxO samples were synthesized via standard solid-state reaction route with Co molar concentrations up to 15 at.%. Magnetic characterization demonstrates a room temperature ferromagnetic behavior associated to a paramagnetic Curie–Weiss component. Detailed microstructural analysis was carried out to exclude the presence of extrinsic sources of ferromagnetism. The magnetization increases linearly as a function of Co concentration. Hall measurements reveal an insulating character for the whole set of samples. In this context, the defect mediated magnetic coupling between the Co atoms under the scope of the bound magnetic polarons model is used to interpret the observed room temperature ferromagnetism.

► High-quality Co-doped ZnO samples were prepared by solid state reaction method.
► Structural defects were introduced by a post-annealing (Ar-95% + H2-5%, 3 h/600 °C).
► After the annealing a room temperature ferromagnetic (RTFM) phase is observed.
► The magnetization saturation presents a linear dependence on Co content.
► RTFM is interpreted in the scope of BMP theory.