Room-temperature ferromagnetism of Mn doped ZnO aligned nanowire arrays with temperature dependent growth

Aligned one-dimensional diluted magnetic semiconductor Zn1-xMnxO nanowires were synthesized from a reaction of metallic Zn foil and MnCl2 center dot 6H(2)O under oxygen environment at variant temperatures between 750 and 950 degrees C by a chemical vapor deposition method. The c-axis preferentially grown nanowire arrays are single crystalline wurtzite structure, of which the growing temperature has a significant influence on both morphology and magnetic ordering. Nanowires with the highest aspect ratios were grown at 850 degrees C, whereas nanowires presenting largest room-temperature ferromagnetism were formed at 950 degrees C. More Mn2+ substitution in the ZnO lattice was observed at 950 degrees C, resulting in strong room-temperature ferromagnetism with a saturation magnetization of 0.25 emu/g. At synthesis temperatures of 750 and 850 degrees C, formation of a ZnMn2O4 room-temperature paramagnetic second phase was found. The nanostructures with different aspect ratios were obtained with the variation of synthesis temperature. The temperature dependent growth of aligned Zn1-xMnxO nanowires reveals strong room-temperature ferromagnetism occurs in the nanowire arrays synthesized at high temperature. The nanowires with strong room temperature have great potential in spintronic nanodevice application. (c) 2007 American Institute of Physics.