Absence of ferromagnetism in Co-doped ZnO prepared by thermal diffusion of Co atoms

Abstract

Thermal diffusion was used to dope Co atoms into ZnO single crystal. Particle-induced x-ray emission combined with channeling technique, x-ray diffraction, and ultraviolet-visible light absorption show that Co-diffused ZnO is pure single-phase alloy. The temperature variation of magnetization can be fitted by a linear combination of the Curie law and the Curie-Weiss law with negative Curie-Weiss temperature (−175K). In the high temperature region, the Co-doped ZnO layer is paramagnetic. In the low temperature region, antiferromagnetism and paramagnetism coexist. Evidence of ferromagnetic hysteresis behavior was not observed down to 5K.