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

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Two series of experiments on wellcharacterized systems were performed to examine the probing depth of soft x-ray absorption spectroscopy (XAS) measured in total-electron-yield (TEY) mode. First we measured the Ni 2p,,, absorption spectra of Ni(100) covered with Tb as a function of the overlayer thickness. Secondly we recorded the 0 Is absorption spectra of Ta,O, films produced by controlled anodic oxidation of Ta foils as a function of the oxide thickness. The mean probing depth (MPD) was found to be much shorter than previously assumed (for 0 Is, only 1.9 nm). The relative importance of those cascade mechanisms that lead to the electron current measured in TEY is discussed.

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