Formation of room-temperature ferromagnetic Zn1−xCoxO nanocrystals

Optical and magnetic properties of Co2+-doped ZnO nanocrystals were studied. Optical measurements confirm the incorporation of Co2+ in ZnO lattice with tetrahedral geometry. Optical absorption spectra also reveal the partial bleaching of the excitonic feature attributable to an increase in electron concentration. Magnetization measurements indicate the ferromagnetic ordering in Co2+-doped ZnO nanocrystals with saturation magnetization 0.75μB/Co. No structural changes were observed in lightly doped ZnO nanocrystals. The present investigations are important in obtaining the ferromagnetic Zn1−xCoxO nanocrystals.