High temperature investigation of the magnetization behavior in cobalt substituted ZnO

High temperature magnetization studies (up to 650°C) of the chemically synthesized nanocrystalline Zn0.9Co0.1O samples are reported in this paper. A systematic study of sequentially sintered sample has been carried out to correlate the observed changes in magnetic behavior vis à vis very small changes in the unit-cell dimensions, evolution of cobalt oxide phases, and absence of Co clusters. The Curie temperature of cobalt substituted ZnO is determined to be ∼495°C. A plausible explanation of the observed room temperature ferromagnetism is presented in terms of bound magnetic polarons model.