Temperature and thickness dependence of magnetic moments in NiO epitaxial films

We show that linear polarized x-ray-absorption spectroscopy can be used to measure the temperature and thickness dependence of magnetic moments in NiO thin films. We demonstrate that both the long-range order and the nearest-neighbor spin-spin correlations can be revealed. NiO (100) films with thicknesses of 5, 10, and 20 monolayers epitaxially grown on MgO (100) are studied. The Neel temperature is found to be strongly reduced from the bulk value even for the 20 monolayer film.