The coupled electronic-structural modulations of the ligand states in IrTe2 have been studied by x-ray absorption spectroscopy (XAS) and resonant elastic x-ray scattering (REXS). Distinctive preedge structures are observed at the Te-M4,5 (3d → 5p) absorption edge, indicating the presence of a Te 5p -Ir 5d covalent state near the Fermi level. An enhancement of the REXS signal near the Te 3d → 5p resonance at the Q = (1/5, 0, −1/5) superlattice reflection is observed below the structural transition temperature Ts ∼ 280 K. The analysis of the energy-dependent REXS lineshape reveals the key role played by the spatial modulation of the covalent Te 5p -Ir 5d bond-density in driving the stripe-like order in IrTe2, and uncovers its coupling with the charge and/or orbital order at the Ir sites. The similarity between these findings and the charge-ordering phenomenology observed in the high-Tc superconducting cuprates suggests that the iridates may harbor similar exotic phases.PACS numbers: 71.45. Lr, 78.70.Ck, 78.70Dm, 71.20.Be Transition-metal compounds exhibit surprisingly rich electronic and magnetic properties due to the partially filled d orbitals. The fundamental properties of the electronic structure of transition-metal compounds can be described within the Zaanen-Sawatzky-Allen (ZSA) scheme. This differentiates between the Mott-Hubbard regime (U < ∆) and the charge-transfer regime (∆ < U ), depending on the relative balance of the on-site Coulomb interaction U between the d electrons and the chargetransfer energy ∆ between the ligand states and the transition-metal d states [1]. When ∆ approaches zero, the ligand states are almost degenerate in energy with the transition-metal d levels. As a result, the ligand states may participate in those spin, charge, and/or orbital ordering phenomena that are peculiar to the correlated nature of the d-orbitals. As an example of such phenomenology, ordering of the oxygen 2p holes is realized in the stripe-ordered phase of layered cuprates [2-6], or in the ladder-type Cu oxides [7].Very recently, a first-order structural transition was discovered in the 5d transition-metal chalcogenide IrTe 2 at T s ∼ 280 K. This attracted great interest due to the concomitant discovery of superconductivity in the Ptand Pd-substituted or intercalated compounds [8, 9]. Clarifying the origin of the structural phase transition might be a critical step towards the understanding of superconductivity itself; however, to date several mechanisms have been debated, with a universal consensus still lacking. The phase transition is accompanied by the emergence of a superstructure lattice modulation in electron diffraction [9] -with wavevector Q = (1/5, 0, −1/5) as expressed in reciprocal lattice units in tetragonal notation -which is here illustrated in Fig. 1. The main elements are the Ir-Ir dimerization along the a axis with period 5a, and the consequent distortion of the triangular Ir sublattice in the a − b plane, conflating to an overall trigonal-to-triclinic symmetry reduction. The IrIr dimeriza...

Thin films of the ferromagnetic metal SrRuO3 (SRO) show a varying easy magnetization axis depending on the epitaxial strain and undergo a metal-to-insulator transition with decreasing film thickness. We have investigated the magnetic properties of SRO thin films with varying thicknesses fabricated on SrTiO3(001) substrates by soft x-ray magnetic circular dichroism (XMCD) at the Ru M2,3 edge. Results have shown that, with decreasing film thickness, the film changes from ferromagnetic to non-magnetic around 3 monolayer thickness, consistent with previous magnetization and magneto-optical Kerr effect measurements. The orbital magnetic moment perpendicular to the film was found to be ∼ 0.1 µB/Ru atom, and remained nearly unchanged with decreasing film thickness while the spin magnetic moment decreases. Mechanism for the formation of the orbital magnetic moment is discussed based on the electronic structure of the compressively strained SRO film.

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Epitaxial CoFe 2 O 4 /Al 2 O 3 bilayers are expected to be highly efficient spin injectors into Si owing to the spin filter effect of CoFe 2 O 4 . To exploit the full potential of this system, understanding the microscopic origin of magnetically dead layers at the CoFe 2 O 4 /Al 2 O 3 interface is necessary. In this paper, we study the crystallographic and electronic structures and the magnetic properties of CoFe 2 O 4 (111) layers with various thicknesses (thickness d = 1.4, 2.3, 4, and 11 nm) in the epitaxial CoFe 2 O 4 (111)/Al 2 O 3 (111)/Si(111) structures using soft X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) combined with cluster-model calculation. The magnetization of CoFe 2 O 4 measured by XMCD gradually decreases with decreasing thickness d and finally a magnetically dead layer is clearly detected at d = 1.4 nm. The magnetically dead layer has frustration of magnetic interactions which is revealed from comparison between the magnetizations at 300 and 6 K. From analysis using configuration-interaction cluster-model calculation, the decrease of d leads to a

We have studied magnetism in anatase Ti1−xCoxO 2−δ (x = 0.05) thin films with various electron carrier densities, by soft x-ray magnetic circular dichroism (XMCD) measurements at the Co L2,3 absorption edges. For electrically conducting samples, the magnetic moment estimated by XMCD was < 0.3 µB/Co using the surface-sensitive total electron yield (TEY) mode, while it was 0.3-2.4 µB/Co using the bulk-sensitive total fluorescence yield (TFY) mode. The latter value is in the same range as the saturation magnetization 0.6-2.1 µB/Co deduced by SQUID measurement. The magnetization and the XMCD intensity increased with carrier density, consistent with the carrierinduced origin of the ferromagnetism.Semiconductors partially substituted with magnetic ions are called diluted magnetic semiconductors (DMSs) and are expected to be useful in spintronics devices, where electron spins can be controlled by electric field and/or by photons. Ferromagnetic DMS's with Curie temperatures (T C 's) higher than room temperature are highly desirable for the development of spintronic devices. To date, much work in this area has been done, mainly on II-VI and III-V compounds doped with magnetic ions such as (Cd,Mn)Te [1] and (Ga,Mn)As [2,3], but their T C

BiFeO3 (BFO) shows both ferroelectricity and magnetic ordering at room temperature but its ferromagnetic component, which is due to spin canting, is negligible. Substitution of transitionmetal atoms such as Co for Fe is known to enhance the ferromagnetic component in BFO. In order to reveal the origin of such magnetization enhancement, we performed soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD) studies of BiFe1−xCoxO3 (x = 0 to 0.30) (BFCO) thin films grown on LaAlO3(001) substrates. The XAS results indicated that the Fe and Co ions are in the Fe 3+ and Co 3+ states. The XMCD results showed that the Fe ions show ferromagnetism while the Co ions are antiferromagnetic at room temperature. The XAS and XMCD measurements also revealed that part of the Fe 3+ ions are tetrahedrally co-ordinated by oxygen ions but that the XMCD signals of the octahedrally coordinated Fe 3+ ions increase with Co content. The results suggest that an impurity phase such as the ferrimagnetic γ-Fe2O3 which exists at low Co concentration decreases with increasing Co concentration and that the ferromagnetic component of the Fe 3+ ion in the octrahedral crystal fields increases with Co concentration, probably reflecting the increased canting of the Fe 3+ ions.

In order to investigate the mechanism of ferromagnetic ordering in the new n-type magnetic semiconductor (In,Fe)As codoped with Be, we have performed x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) studies of ferromagnetic and paramagnetic samples. The spectral line shapes suggest that the ferromagnetism is intrinsic, originating from Fe atoms incorporated into the zinc-blende-type InAs lattice. The magnetization curves of Fe measured by XMCD were well reproduced by the superposition of a Langevin function representing superparamagnetic (SPM) behavior of nanoscale ferromagnetic domains and a T -linear function representing Curie-Weiss paramagnetism even much above the Curie temperatures. The data at 20 K showed a deviation from the Langevin behavior, suggesting a gradual establishment of macroscopic ferromagnetism on lowering temperature. The existence of nanoscale ferromagnetic domains indicated by the SPM behavior suggests spatial fluctuations of Fe concentration on the nanoscale.

Magnetic anisotropies of ferromagnetic thin films are induced by epitaxial strain from the substrate via strain-induced anisotropy in the orbital magnetic moment and that in the spatial distribution of spin-polarized electrons. However, the preferential orbital occupation in ferromagnetic metallic La 1−x Sr x MnO 3 (LSMO) thin films studied by x-ray linear dichroism (XLD) has always been found out-of-plane for both tensile and compressive epitaxial strain and hence irrespective of the magnetic anisotropy. In order to resolve this mystery, we directly probed the preferential orbital occupation of spin-polarized electrons in LSMO thin films under strain by angle-dependent x-ray magnetic circular dichroism (XMCD). Anisotropy of the spin-density distribution was found to be in-plane for the tensile strain and out-of-plane for the compressive strain, consistent with the observed magnetic anisotropy. The ubiquitous out-of-plane preferential orbital occupation seen by XLD is attributed to the occupation of both spin-up and spin-down out-ofplane orbitals in the surface magnetic dead layer.