Room temperature ferromagnetism in Co doped ZnO within an optimal doping level of 5%

We report on the structural, micro-structural and magnetic properties of Zn1−xCoxO (0 ≤ x ≤ 0.1) system. Electron probe micro-structural analysis on 5% Co doped ZnO indicates the presence of segregated cobalt oxide which is also confirmed from the Co 2p core level X-ray photoelectron spectrum. The presence of oxygen defects in lower percentage of Co doped ZnO (≤5%) enhances the carrier mediated exchange interaction and thereby enhancing the room-temperature ferromagnetic behaviour. Higher doping percentage of cobalt (>5%) creates weak link between the grains and suppresses the carrier mediated exchange interaction. This is the reason why room temperature ferromagnetism is not observed in 7% and 10% Co doped ZnO.

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► Zn1−xCoxO ((0 ≤ x ≤ 0.1)) system synthesized by solid state reaction technique.
► Observation of room temperature ferromagnetism for 3 and 5% Co doped ZnO.
► XPS and EPMA studies predict the occurrence of segregated CoO clusters.
► Suppresses ferromagnetic ordering in higher doping percentage of Co (>5%).