Room-temperature ferromagnetism in Co-doped ZnO bulk induced by hydrogenation

The room-temperature ferromagnetism properties of Co-doped zinc oxide are reported in this paper. The Zn1-xCoxO (0.02 < x < 0.10)specimens were synthesized by the solid state reaction method with the mixture of Co2O3 and ZnO powders. The precursor Co2O3 and ZnO powders were mixed and milled for 10 h. The mixed powders were calcined at temperature of 600 degrees C and 1000 degrees C, respectively for 12 h, and then were cooled at the ambient temperature. Next, the powders were milled, made block and sintered for 12 h. The specimens were then hydrogenated at 600 degrees C for 1 h and 3 h, respectively. The room-temperature ferromagnetism (RTFM) was found in the hydrogenated samples, and the hysteresis loops of the hydrogenated Co-doped ZnO samples were measured at 10 K and 300 K by using the superconducting quantum interference device (SQUID) magnetometer (Quantum Design). The coercive field was about 310 Oe for the room-temperature measurement, and the saturation magnetization of the hydrogenated sample was about 0.056 mu(B)/Co. The samples were further measured by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The results suggested the observed RTFM in the Co-doped ZnO was partly due to the existence of the cobalt nanoparticles in the hydrogenated samples. (c) 2006 Elsevier B.V. All rights reserved.