Origin of the ferromagnetism in ZnCoO from chemical reaction of Co₃O₄

다국어 초록 (Multilingual Abstract)

We investigated conversion of Co<SUB>3</SUB>O<SUB>4</SUB> to Co nanoclusters through hydrogen reduction. Quantitative analysis is performed on the conversion of Co<SUB>3</SUB>O<SUB>4</SUB> to Co metal as a function of hydrogen-injection conditions. Our results reveal that Co<SUB>3</SUB>O<SUB>4</SUB> must be completely eliminated to avoid formation of the metal phase in ZnCoO. We also propose a new M-T curve based method for detecting nano-sized Co clusters which are below the detection limit of diffraction techniques. It is also found that the Co phase can be transformed back to the Co<SUB>3</SUB>O<SUB>4</SUB> phase through oxygen annealing and that, as a result, the ferromagnetism can be eliminated. These findings are discussed in the context of the origin of ferromagnetism in ZnCoO.