Ferromagnetic Zn_1-xMn_xO (x = 0.05, 0.1, and 0.2) nanowires

Single-crystalline Zn_1-xMn_x;O (x = 0.05, 0.1, and 0.2) nanowires were synthesized using the thermal vapor transport method. Their X-ray diffraction patterns reveal the monotonous expansion of the lattice constants with increasing Mn content, due to the effective Mn doping. The electronic structures of the Zn and Mn atoms were probed by X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD), in order to investigate the origin of their ferromagnetism. As the Mn content increases to x = 0.1, the XPS peaks of Zn and Mn 2p shift to a higher energy, suggesting the possibility of hybridization between the Mn²⁺ ions and host defects. The XAS and XMCD spectra confirm that the Mn2+ ions substitute into the tetrahedrally coordinated Zn sites in ZnO. The magnetization curves indicate the existence of room-temperature ferromagnetic behavior. The magnetoresistance of a single Zn_0.9Mn_0.1O nanowire reaches a positive value of 10% at 2 K under a magnetic field of 9 T.