Magnetic circular dichroism of ferromagnetic Co2+-doped ZnO

Cobalt-doped ZnO (Co2+:ZnO) films were studied by magnetic circular dichroism (MCD) spectroscopy. A broad 300K ferromagnetic MCD signal was observed between 1.4 and 4.0eV after exposure of paramagnetic Co2+:ZnO films to zinc metal vapor, attributed to low-energy photoionization transitions originating from a spin-split donor impurity band in ferromagnetic n-type Co2+:ZnO.