A quantum explanation of the abnormal magnetic behaviour in Mn-doped ZnO nanowires

The effective mass approximation is applied to explain the abnormal magnetic behaviour observed recently in Mn-doped ZnO nanowires. The magnetization versus temperature curves have been calculated for nanowires at different radii and carrier densities. Abnormal peaks in the M-T curves are observed at low temperature when the radii of the cylinders are in the nanometre region. Peaks have been observed in the calculated M-T curves for some carrier densities where the Fermi levels are near the peaks of the majority spins in the density of states ( DOS) plots, and the peak position moves to the high-temperature region when the radius of the nanowire decreases. The abnormal magnetic peaks in the M-T curve can be explained as a quantum confinement effect of nanowires.