论文部分内容阅读
Zn1-xCoxO(x=0.01,0.02,0.05,0.10 and 0.20) diluted magnetic semiconductors are prepared by the sol-gel method.The structural and magnetic properties of the samples are studied using x-ray diffraction(XRD),extended x-ray absorption fine structure (EXAFS) and superconducting quantum interference device(SQUID).The XRD pattes does not show any signal of precipitates that are different from wurtzite type ZnO when Co content is lower than x=0.10.An EXAFS technique for the Co K-edge has been employed to probe the local structures around Co atoms doped in ZnO powders by fluorescence mode.The simulation results for the first shell EXAFS signals indicate that Zn sites can be substituted by Co atoms when Co content is lower than x=0.05.The SQUID results show that the samples (x<0.05)exhibit clear hysteresis loops at 300K,and magnetization versus temperature from 5K to 350K at H=100 Oe for the sample x=0.02 shows that the samples have ferromagnetism above room temperature.A double-exchange mechanism is proposed to explain the ferromagnetic properties of the samples.