Study of electronic and magnetic properties of vacuum annealed Cr doped ZnO

Influence of Cr doping (5%) in ZnO lattice has been investigated in terms of modifications in electronic properties, evolution of defects and exploring their possible relationship with magnetic properties, using SQUID magnetometry and X-ray photoelectron spectroscopy (XPS). The Cr doping drives the diamagnetic ZnO host to a paramagnetic state, however, its post annealing in vacuum induces room temperature ferromagnetism (RTFM) in it that disappears by re-heating it in air. The findings infer a reversible ferromagnetic ordering in the Cr doped ZnO matrix. The XPS results indicate trivalent state of the Cr ions in the as-synthesized sample which tend to reduce to bivalency upon its vacuum annealing and also the evolution of oxygen vacancy defects have clearly been observed. The results indicate a close relationship of oxygen vacancies with the induced ferromagnetism.

► Evolution of ferromagnetism in Cr doped ZnO on vacuum annealing.
► The ferromagnetism is a reversible process.
► Electronic properties and ferromagnetism are closely related.
► Oxygen vacancies are very crucial in inducing ferromagnetism.