High-temperature ferromagnetism in (Co, Al)-codoped ZnO powders

Zn 0.95 − x Co 0.05 Al x O (x=0,0.01,0.03) powders were prepared from the acetate-derived precursor by the sol-gel route. The structural and magnetic properties of the powders were investigated. X-ray absorption spectroscopy and high-resolution transmission electron microscope analyses indicate that Co2+ substitute for Zn2+ without changing the wurtzite structure. The powder shows paramagnetic behavior at 5K for x=0 sample. For x=0.01 and 0.03, the powders exhibit ferromagnetic behavior at 360K. It was demonstrated experimentally that high-temperature ferromagnetism in Co-doped ZnO powders can be obtained through increasing the carrier concentration which was realized by doping a few percent of Al.