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SmFeO3 has attracted considerable attention very recently due to its reported multiferroic properties above room temperature. We have performed powder and single crystal neutron diffraction as well as complementary polarization dependent soft X-ray absorption spectroscopy measurements on floating-zone grown SmFeO3 single crystals in order to determine its magnetic structure. We found a k = 0 G-type collinear antiferromagnetic structure that is not compatible with inverse Dzyaloshinskii-Moriya interaction driven ferroelectricity. While the structural data reveal a clear sign for magneto-elastic coupling at the Neel-temperature of ∼675 K, the dielectric measurements remain silent as far as ferroelectricity is concerned. [ABSTRACT FROM AUTHOR]

We studied the local Ru 4d electronic structure of α-RuCl3 by means of polarization-dependent x-ray absorption spectroscopy at the Ru L2,3 edges. We observed a vanishingly small linear dichroism indicating that electronically the Ru 4d local symmetry is highly cubic. Using full multiplet cluster calculations we were able to reproduce the spectra excellently and to extract that the trigonal splitting of the t2g orbitals is -12 ± 10 meV, i.e., negligible as compared to the Ru 4d spin-orbit coupling constant. Consistent with our magnetic circular dichroism measurements, we found that the ratio of the orbital and spin moments is 2.0, the value expected for a Jeff = 1/2 ground state. We have thus shown that as far as the Ru 4d local properties are concerned, α-RuCl3 is an ideal candidate for the realization of Kitaev physics. [ABSTRACT FROM AUTHOR]

We report on a combined soft x-ray absorption and magnetic circular dichroism (XMCD) study at the Co-L3,2 edge on the hybrid 3d/5d solid state oxide Sr2Co0.5Ir0.5O4 with K2NiF4 structure. Our data indicate unambiguously a pure high spin state (S=2) for the Co3+ (3d6) ions with a significant unquenched orbital moment Lz/2Sz=0.25 despite the sizable elongation of the CoO6 octahedra. Using quantitative model calculations based on parameters consistent with our spectra, we have investigated the stability of this high spin state with respect to the competing low spin and intermediate spin states. [ABSTRACT FROM AUTHOR]

We have studied the magnetic properties and the underlying type of orbital ordering in the layered hybrid organic-inorganic compound (C6H5CH2CH2NH3)2CuCl4 by using ac-magnetic susceptibility and polarization-dependent soft-x-ray absorption spectroscopy at the Cu-L2 and Cu-L3 edges. We have established that the compound has a long-range ferromagnetic ordering both in plane and out of plane and we found from the analysis of the absorption spectra that the orbital ordering of the Cu2+ holes involves the cross-type dx2-z²/dy²-z² arrangement which is different from the dx2-y² arrangement found in the parent compounds of the high-Tc cuprate superconductors. [ABSTRACT FROM AUTHOR]

We report a study of the local magnetism in thin films of SrRuO3 grown on (111) and (001) oriented SrTiO3 substrates using x-ray magnetic circular dichroism spectroscopy (XMCD) at the Ru-L2,3 edges. The application of the sum rules to the XMCD data gives an almost quenched orbital moment and a spin moment close to the value expected for the low spin state S=1. Full-multiplet cluster calculations indicate that the low spin state is quite stable and suggest that the occurrence of a transition to the high spin state S=2 in strained thin films of SrRuO3 is unlikely as it would be too expensive in energy. [ABSTRACT FROM AUTHOR]

The changes of physical properties occurring at a first-order-like transition among a wide family of (Pr1-yLny)1-xCaxCoO3 compounds (Ln being a lanthanide) are controversially discussed as a transition of Co3+ ions from states of low spin (LS) to intermediate spin (IS), or from LS to a mixture of LS and high spin (HS). The debate also includes the nature of the spin state of Co4+, as well as the degree of valence shift between Pr3+ and Pr4+ which accompanies this transition. In the present paper, we investigated the evolution of spin and valence states of Co ions and the valence state of Pr ions in (Pr0.7Sm0.3)0.7Ca0.3CoO 3 , at high temperature up to 750 K and under pressure up to 36.5 GPa. For this purpose, the data of three spectroscopic techniques were combined: high-resolution Co K-edge partial-fluorescence-yield x-ray absorption spectra, Pr L2-edge x-ray absorption spectra, and Co K β x-ray emission spectra. The spectral weight transfer of the pre-edge peaks of the Co K-edge spectra reveals a continuous redistribution of 3d electrons between the t2g and eg levels of Co ions, reflecting a gradual increase of the average Co spin state upon heating. This is further confirmed by Co K β x-ray emission spectra, which show an increase of HS Co3+ population when increasing temperature from 300 to 750 K. Applying high pressure at 300 K, the Co K β x-ray emission spectra indicate a relatively sharp increase of LS Co3+ population below 4 GPa. Pr L2-edge x-ray absorption spectra of (Pr0.7Sm0.3)0.7Ca0.3CoO3 exhibit a valence-state transition from Pr3+ to Pr3.26+, occurring predominantly upon applying pressure in the range ~ 4 to ~ 12 GPa. Owing to the charge balance, increasing pressure in this regime induces complex valence and spin-state transitions within the Co ions. Moreover, at high enough pressure, it is found that the Co4+ can also undergo a spin-state transition (from IS to LS), in addition to that affecting the Co3+ (HS to LS). [ABSTRACT FROM AUTHOR]

We present a combined experimental and theoretical study on the local magnetism of the Co ions in the spin-chain compound CoV2O6, which crystallizes in two different allotropic phases, α- and γ-CoV2O6. Using x-ray magnetic circular dichroism, we have found an exceptionally high and a moderate orbital contribution to the magnetism in α-CoV2O6 and γ-CoV2O6, respectively. Full-multiplet calculations indicate that the differences in the magnetic behavior of α- and γ-CoV2O6 phases originate from different local distortions of the Co06 octahedra. In particular, the strong compression of the CoO6 octahedra together with the unusually small octahedral crystal field splitting in α-CoV2O6 lead to a strong mixture of t2g and eg orbitals which, via the local atomic Coulomb and exchange interactions, results in an exceptionally large orbital moment. [ABSTRACT FROM AUTHOR]

Here we present linear-polarization-dependent soft x-ray absorption spectroscopy data at the Ce M4,5 edges of CeOs2Al10 and CeFe2Al10. Despite the strong hybridization between 4f and conduction electrons and the existence of spin gaps as seen in inelastic neutron scattering, we were able to determine the crystal field ground state wave functions by combining our spectroscopy data with magnetization measurements. The results quantitatively explain the small ordered moment along c and the measured magnetic moment along the easy a axis in CeOs2Al10. [ABSTRACT FROM AUTHOR]

The coupled valence and spin state transition (VSST) taking place in (Pr0.7Sm0.3)0.7Ca0.3CoO3 was investigated by soft x-ray absorption spectroscopy (XAS) experiments carried out at the Pr-M4,5, Co-L2,3, and O-1s edges. This VSST is found to be composed of a sharp Pr/Co valence and Co spin state transition centered at T* ~ 89.3 K, followed by a smoother Co spin-state evolution at higher temperatures. At T < T*, we found that the praseodymium displays a mixed valence Pr3+/Pr4+ with about 0.13 Pr4+/f.u., while all the Co3+ is in the low-spin (LS) state. At T~T*, the sharp valence transition converts all the Pr4+ to Pr3+ with a corresponding Co3+ to Co4+ compensation. This is accompanied by an equally sharp spin state transition of the Co3+ from the low to an incoherent mixture of low and high-spin (HS) states. An involvement of the intermediate-spin (IS) state can be discarded for the Co3+. While above T* and at high temperatures the system shares rather similar properties as Sr-doped LaCoO3, at low temperatures, it behaves much more like EuCoO3 with its highly stable LS configuration for the Co3+. Apparently, the mechanism responsible for the formation of Pr4+ at low temperatures also helps to stabilize the Co3+ in the LS configuration despite the presence of Co4+ ions. We also found out that that the Co4+ is in an IS state over the entire temperature range investigated in this study (10-290 K). The presence of Co3+ HS and Co4+ IS at elevated temperatures facilitates the conductivity of the material. [ABSTRACT FROM AUTHOR]

A new orthorhombic phase of the multiferroic BiFeO3 has been created via strain engineering by growing it on a NdScO3(110)o substrate. The tensile-strained orthorhombic BiFeO3 phase is ferroelectric and antiferromagnetic at room temperature. A combination of nonlinear optical second harmonic generation and piezoresponse force microscopy revealed that the ferroelectric polarization in the orthorhombic phase is along the in-plane <110>pc directions. In addition, the corresponding rotation of the antiferromagnetic axis in this new phase was observed using x-ray linear dichroism. [ABSTRACT FROM AUTHOR]

Ba2Co9O14 is a charge-ordered Co2+/3+ cobaltite that consists of building blocks of Cdl2-type Co2+/3+O6/3 layers, face-shared Co3+3O12 octahedral trimers, and corner-sharing Co2+04 tetrahedra. The Co-L2,3 x-ray absorption spectroscopy spectrum at room temperature indicates a high and a low spin state for Co2+ and Co3+ ions, respectively. Measurements of high-temperature resistivity and thermoelectric power revealed an insulator-to-insulator phase transition at Tt = 570 K, above which the inverse magnetic susceptibility X-1(T) deviates from the Curie-Weiss law. By using a combination of soft x-ray absorption spectroscopy at the O-K edge and high-resolution synchrotron x-ray powder diffraction measurements on crossing Tt, we have successfully determined the origin of this phase transition as a low-to-higher spin-state transition of Co3+ ions within the face-shared Co3O12 octahedral trimers in Ba2Co9O14. [ABSTRACT FROM AUTHOR]

We report direct experimental evidence for a room-temperature, ~130 µC/cm² ferroelectric polarization from the tetragonal-like BiFeO3 phase. The physical origin of this remarkable enhancement of ferroelectric polarization has been investigated by a combination of x-ray absorption spectroscopy, scanning transmission electron microscopy, and first principles calculations. A large strain-induced Fe-ion displacement relative to the oxygen octabedra, combined with the contribution of Bi 6s lone pair electrons, is the mechanism driving the large ferroelectric polarization in this tetragonal-like phase. [ABSTRACT FROM AUTHOR]

A correction to the article "Crystal field ground state of the orthorhombic Kondo semiconductors CeOs2Al10 and CeFe2Al10" that was published in the 2013 issue is presented.