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C2D6 measured with unprecedent energy resolution and signal-to-noise ratio are presented. These spectra reveal many new features in core-excited valence and Rydberg states. Detailed vibrational structures are observed in these spectra, providing valuable information on the geometrical and vibrational properties of the core-excited molecules. In addition, C 1s and N 1s core-hole lifetimes are found to be -120 and -135 meV in these molecules with little dependence on their bonding environments. These results and the tentative peak assignments are discussed briefly in terms of the equivalent core model, multielectron excitations, exchange interactions, and the geometry of the excited molecules.

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 ...

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Strong resonant enhancements of the charge-order and spin-order superstructure-diffraction intensities in La1.8Sr0.2NiO4 are observed when x-ray energies in the vicinity of the Ni L2,3 absorption edges are used. The pronounced photon-energy and polarization dependences of these diffraction intensities allow for a critical determination of the local symmetry of the ordered spin and charge carriers. We found that not only the antiferromagnetic order but also the charge-order superstructure resides within the NiO2 layers; the holes are mainly located on in-plane oxygens surrounding a Ni2+ site with the spins coupled antiparallel in close analogy to Zhang-Rice singlets in the cuprates.