Room-temperature ferromagnetism in lightly Cr-doped ZnO nanoparticles

Zn1−xCrxO (0≤x≤0.15) nanoparticles were synthesized by an auto-combustion method and characterized by x-ray diffraction and Raman scattering techniques. The solubility limit for Cr in ZnO was determined as x≈0.03. Room-temperature ferromagnetism (RT-FM) was observed in lightly Cr-doped ZnO nanoparticles with x=0.01 and 0.02. Raman scattering spectra of the lightly Cr-doped and Co-doped ZnO were studied and compared. The enhancement of both the magnetization and the intensity of Raman scattering peak associated with donor defects (Zni and/or VO) and carriers indicates that light Cr doping in ZnO could be an effective way to achieve pronounced RT-FM and the ferromagnetism is closely related to the dopant-donor hybridization besides the ferromagnetic Cr–O–Cr superexchange interactions.