We report on a systematic analysis of x-ray photoelectron spectroscopy ͑XPS͒ core-and valence-level spectra of clean and well-characterized iron oxide films, i.

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

We report spin-polarized transport experiments across antiphase domain boundaries which act as atomically sharp magnetic interfaces. The antiphase boundaries are prepared by growing Fe(3)O(4) epitaxially on MgO, the magnetic coupling over a large fraction of these boundaries being antiferromagnetic. Magnetoresistance measurements yield linear and quadratic field dependence up to the anisotropy field for fields applied parallel and perpendicular to the film plane, respectively. This behavior can be explained by a hopping model in which spin-polarized electrons traverse an antiferromagnetic interface between two ferromagnetic chains.

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We have observed that CoO films grown on different substrates show dramatic differences in their magnetic properties. Using polarization dependent x-ray absorption spectroscopy at the Co L2,3 edges, we revealed that the magnitude and orientation of the magnetic moments strongly depend on the strain in the films induced by the substrate. We presented a quantitative model to explain how strain together with the spin-orbit interaction determine the 3d orbital occupation, the magnetic anisotropy, as well as the spin and orbital contributions to the magnetic moments. Control over the sign and direction of the strain may therefore open new opportunities for applications in the field of exchange bias in multilayered magnetic films.The discovery of the exchange bias phenomenon in surface-oxidized cobalt particles about 50 years ago [1] marks the beginning of a new research field in magnetism. Since then several combinations of antiferromagnetic (AFM) and ferromagnetic (FM) thin film materials have been fabricated and investigated [2,3], motivated by the potential for applications in information technology. Numerous theoretical [4,5,6,7,8] and experimental [9,10,11,12,13,14] studies have been devoted to unravel the mechanism(s) responsible for exchange biasing. However, no conclusive picture has emerged yet. A major part of the problem lies in the fact that there is insufficient information available concerning the atomic and magnetic structure of the crucial interface between the AFM and FM material. The important issue of, for instance, spin reorientations in the AFM films close to the interface is hardly considered [15,16,17,18,19], and the role of epitaxial strain herein has not been discussed at all.In this paper we study the magnetic properties of CoO thin films epitaxially grown on MnO(100) and on Ag(100), as model systems for an AFM material under either tensile or compressive in-plane stress. Our objective is to establish how the magnetic anisotropy as well as the spin and orbital contributions to the magnetic moments depend on the lowering of the local crystal field symmetry by epitaxial strain. Using polarization dependent x-ray absorption spectroscopy (XAS) at the Co L 2,3 (2p → 3d) edges, we observe that the magnitude and orientation of the magnetic moments in the CoO/MnO(100) system are very different from those in the CoO/Ag(100). We present a quantitative model to calculate how local crystal fields together with the spin-orbit interaction determine the magnetic properties. to 10 −6 mbar. The base pressure of the MBE system is in the low 10 −10 mbar range. The thickness and epitaxial quality of the films are monitored by reflection high energy electron diffraction measurements. With the lattice constant of bulk Ag (4.09Å) being smaller than that of bulk CoO (4.26Å) and MnO (4.444Å), we find from x-ray diffraction that CoO on Ag is slightly compressed in-plane (a ≈ 4.235Å, a ⊥ ≈ 4.285Å), and from reflection high energy electron diffraction (RHEED) that CoO sandwiched by MnO is about 4% expanded in-plane (a ...