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The nature of the electronic groundstate of Ba2IrO4 has been addressed using soft X-ray absorption and inelastic scattering techniques in the vicinity of the oxygen K edge. From the polarization and angular dependence of XAS we deduce an approximately equal superposition of xy, yz and zx Ir4+ 5d orbitals. By combining the measured orbital occupancies, with the value of the spin-orbit coupling provided by RIXS, we estimate the crystal field splitting associated with the tetragonal distortion of the IrO6 octahedra to be small, \Delta=50(50) meV. We thus conclude definitively that Ba2IrO4 is a close realization of a spin-orbit Mott insulator with a jeff = 1/2 groundstate, thereby overcoming ambiguities in this assignment associated with the interpretation of X-ray resonant scattering experiments., Comment: 5 pages, 5 figures

The spin and orbital configuration of magnetic metal phthalocyanines (MPcs) deposited on metallic substrates are strongly influenced by the rehybridization of the molecular states with the underlying metal. FePc, CoPc, and CuPc isolated molecules are archetypal systems to investigate the interrelationship between magnetic moments and orbital symmetry after deposition on a metallic substrate. MPcs form long-range ordered chains self-assembled along the reconstructed channels of the Au(110) surface. X-ray magnetic circular dichroism from the ${L}_{2,3}$ absorption edges of Fe, Co, and Cu shows that the orbital and spin configuration are strongly modified upon adsorption on the Au(110) surface if the orbitals responsible of the magnetic moment are involved in the interaction process. The magnetic moment for a single layer of molecular chains is completely quenched for the CoPc molecules, fully preserved for the CuPc and reduced for the FePc ones. The modified magnetic configuration is confined to the very interface layer, i.e., to the MPc molecules bound to the metal substrate up to the compact packing of the single layer. The different response can be rationalized in terms of the symmetry/orientation of the metal-ion $d$ states interacting with the substrate states, as indicated by density functional theory calculations in agreement with experimental findings.

We demonstrate that the growth of Fe/(Ga,Mn)As heterointerfaces can be efficiently controlled by epitaxy and that robust ferromagnetism of the interfacial Mn atoms is induced at room temperature by the proximity effect. X-ray magnetic circular dichroism and x-ray resonant reflectivity data, supported by theoretical calculations, were used to monitor both temperature and magnetic field dependence of the Mn magnetic moment in the semiconducting host. We identify distinct Mn populations, each of them with specific magnetic character.

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We describe a new spectrometer for spin resolved photoemission from solids in the soft x-ray energy range. It is mounted on the ID08 beamline at the ESRF light source and consists of a time-of-flight (TOF) energy analyzer coupled to a retarding mini-Mott spin polarimeter. It represents a valid alternative to the spin detection system already available on ID08, especially for the acquisition of wide energy regions, where the TOF technique is extremely efficient. By testing the new spectrometer on the 4f levels of Au and on CuO at the Cu L-3 threshold we show that the effective Sherman function and figure of merit achieved are, respectively, S-eff similar or equal to 0.16 and eta similar or equal to 1.3 x 10(-4) and that for certain experiments we obtain a significant gain in intensity with respect to the previous system. (C) 2008 American Institute of Physics.

Resonant inelastic x-ray scattering (RIXS) measurements performed jointly across the M-2,M-3 and L-3 absorption thresholds are used to study CoO local electronic structure and are supported by model calculations. The high-resolution experimental data provide a precise set of parameters to describe the correlated response of valence electrons. The same core-hole independent set of parameters within the single impurity Anderson model is used to describe both the M (3p-3d) and L (2p-3d) resonances. This work shows that combining M and L scattering data provides an enhanced contrast view of the spectral weights. Measured M-2,M-3-RIXS spectra are observed to be free of charge-transfer or normal fluorescence contributions. Moreover the cross section of M-RIXS final states with change in spin multiplicity is low. Combining this information with L-edge studies establishes an appealing means of making a better separation between on-site and intersite (ligand to metal) electronic excitations. Experimental and theoretical features specific to RIXS studies performed at M and L edges are summarized as a basis for future studies on complex transition metal compounds.

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. Soft x-ray resonant magnetic scattering has been used to investigate the element-selective microscopic magnetization reversal behavior of room temperature perpendicular exchange coupled ferromagnetic∕antiferromagnetic (F∕AF) systems and to study the role of the interfacial coupling strength on it. Different nucleation processes and domain size distributions along the decreasing and increasing branches of the reversal have been found. The size of the magnetic domains during reversal depends on both the F anisotropy and F∕AF coupling strength, decreasing when one of them increases. Evidence of the exchange bias(coercivity enhancement) being induced by pinned (unpinned) uncompensated AF interfacial spins is also shown.

Utilizing a sum rule in a spin-resolved photoelectron spectroscopic experiment with circularly polarized light, we show that the orbital moment in LaTiO3 is strongly reduced from its ionic value, both below and above the Ne el temperature. Using Ti L2,3 x-ray absorption spectroscopy as a local probe, we found that the crystal-field splitting in the t2g subshell is about 0.12-0.30 eV. This large splitting does not facilitate the formation of an orbital liquid.