Structure、magnetic And Transport Properties Of Mn Doped CuO Diluted Magnetic Semiconductor

Great effort has been devoted since Dietl et al. predicted that high-temperature ferromagnetism could be found in p-type semiconductors via changing carrier and doping concentration. CuO attracts more attention for it is a p-type, direct bandgap oxide semiconductor. First report about ferromagnetism in Mn-doped CuO was in2003. An unconventional double-exchange model, which is consistent with several experimental results,was proposed to explain the FM in Mn-doped CuO. However, high doping density is required in double-exchange model although several studies reported FM in samples with low doping density.To study the origin of the ferromagnetism in Mn-doped CuO, we synthesize poly crystals Cui-xMnxO(x=0,0.06,0.1,0.2) by sol-gel method. Partial Mn atoms are confirmed to enter the CuO lattice and form the Cu1-xMnxO compounds. With increasing the Mn content, an obvious magnetism is observed, and the magnetic moment for each Mn atom increases with the dope concentration from1.94μB/atom to2.66μB/atom to2.77μB/atom. The magnetic critical transition temperature increases to82.3k with the magnetism enhancing, which obey the bound magnetic polaron theory. The electronic transportation shows an insulating behavior, with the band-gap decreases. Our results may indicate that CuO may use as the candidate of magnetic semiconductor.For further study into the relationship of carrier density and magnetism, Cuo.94Mno.06O and Cu0.8Mno.2O samples are pressed into3pieces, and two of them annealed in N2ambient for2hours and4hours, individually. As CuO is p-type semiconductor naturally, annealing in N2may increase the amount of oxygen vacancy and generate electrons to compensate the major carriers, thus the carrier concentration is reduced. Systematically reduction of the saturation moment andCurie temperature of both Cuo.94Mno.06O and Cuo.8Mn0.2O annealing in N2are observed. We find that magnetism properties of Mn-doped CuO may be manipulated by N2annealing, which varies the carrier concentration. This result is quite consistent with the results raised by Dietl. Our results may suggest that ferromagnetism and Curie temperature of Mn-doped CuO may be enhanced by increasing carrier density of the samples. This has important implications for implementation and application of CuO semiconductors.