Defect-induced reversible ferromagnetism in hydrogenated ZnO:Co

Through simple hydrogen annealing treatment, we observed robust inducement of room temperature ferromagnetism (RTFM) in ZnO:Co (5%) pellets. The hydrogen mediated magnetic transition is accompanied by electronic structure plus bonding modifications with no structural deviations or creation of secondary phases, as evidenced by XRD and photoemission investigations. Our findings reveal a route correlation of oxygen vacancies with the observed RTFM. In particular, we systematically investigated the time controlled re-heating consequences on hydrogenated sample. The H-induced RTFM and subsequent modifications viz. electronic structure, transport properties and bonding effect gradually retrace back upon evaporating the hydrogen.