Photovoltage detection of x-ray absorption and magnetic circular dichroism spectra of magnetic films grown on semiconductors

We describe a measurement technique for x-ray absorption spectroscopy, in which the sample is used as the detector. Co L-2,L-3 absorption spectra were taken from cobalt films grown on n-GaAs by measuring the photovoltage generated by the x rays transmitted across the rectifying metal-semiconductor contact. After correcting the effects of signal saturation good agreement was obtained with spectra acquired using the conventional total electron yield method. X-ray magnetic circular dichroism measurements using the method gave values for the spin moment of cobalt between 1.48 and 1.89 mu(B)/atom, compared to the value in the literature of 1.55 mu(B)/atom for the bulk. An anomalously high average value of 0.39 mu(B)/atom was found for the orbital moment and attributed to the presence of oxide in the films.