Increasing coercivity of ferromagnetic zinc oxide with thermal acetylene treatment

We have used a thermal acetylene treatment on ZnO nanorods in order to investigate the possibility of carbon-doping-induced room temperature ferromagnetism in them. The properties of the rods were investigated using SQUID magnetometry and photoelectron spectroscopy and the findings compared to previously reported results. Ferromagnetism was detected in all investigated samples, but no clear correlation between acetylene and the strength of ferromagnetism was observed. A weakening of the hybridization of Zn 3d and O 2p states as a result of acetylene treatment was detected. The coercivity of acetylene-doped samples was observed to be higher than in annealed samples. The findings support the view that ferromagnetism in ZnO is intrinsic in origin and not caused by carbon doping. However, the treatment can still be used to engineer the magnetic properties of the material, as it can tune its surface properties.