Atomic multiplet calculation of 3d_{5/2} -> 4f resonant x-ray diffraction from Ho metal (2008)
Haverkort, M. W., Schüßler-Langeheine, C., Chang, C. F., Buchholz, M., Wu, H. -H., Ott, H., ...
We compare for Ho metal the x-ray absorption spectrum and the resonant soft x-ray diffraction spectra obtained at the $3d_{5/2} \to 4f$ ($M_5$) resonance for the magnetic 1st and 2nd order...
Effective Operator for $dd$ Transitions in Nonresonant Inelastic X-ray Scattering (2008)
Van Veenendaal, Michel, Haverkort, M. W.
Recent experiments by Larson et al. demonstrate the feasibility of measuring local $dd$ excitations using nonresonant inelastic X-ray scattering (IXS). We establish a general framework for the...
Strong spin-orbit coupling effects on the Fermi surface of Sr2RuO4 and Sr2RhO4 (2008)
Haverkort, M. W., Elfimov, I. S., Tjeng, L. H., Sawatzky, G. A., Damascelli, A.
We present a first-principle study of spin-orbit coupling effects on the Fermi surface of Sr2RuO4 and Sr2RhO4. For nearly degenerate bands, spin-orbit coupling leads to a dramatic change of the Fermi...
Crystal-field level inversion in lightly Mn-doped Sr3Ru2O7 (2008)
Hossain, M. A., Hu, Z., Haverkort, M. W., Burnus, T., Chang, C. F., Klein, S., ...
Sr3(Ru1-xMnx)2O7, in which 4d-Ru is substituted by the more localized 3d-Mn, is studied by x-ray dichroism and spin-resolved density functional theory. We find that Mn impurities do not exhibit the...
Anisotropic Susceptibility of La_2-xSr_xCoO_4 related to the Spin States of Cobalt (2008)
Hollmann, N., Haverkort, M. W., Cwik, M., Benomar, M., Reuther, M., Tanaka, A., ...
We present a study of the magnetic susceptibility of La_2-xSr_xCoO_4 single crystals in a doping range 0.3=0.5. This includes the pronounced kinks observed in the inverse magnetic susceptibility,...
High multipole transitions in NIXS: valence and hybridization in 4f systems (2007)
Gordon, R. A., Seidler, G. T., Fister, T. T., Haverkort, M. W., Sawatzky, G. A., Tanaka, A., ...
Momentum-transfer (q) dependent non-resonant inelastic x-ray scattering measurements were made at the N4,5 edges for several rare earth compounds. With increasing q, giant dipole resonances diminish,...
Hansmann, P., Severing, A., Hu, Z., Haverkort, M. W., Chang, C. F., Klein, S., ...
We infer that soft-x-ray absorption spectroscopy is a versatile method for the determination of the crystal-field ground state symmetry of rare earth Heavy Fermion systems, complementing neutron...
Mott-Hubbard versus charge-transfer behavior in LaSrMnO4 studied via optical conductivity (2007)
Gössling, A., Haverkort, M. W., Benomar, M., Wu, H., Senff, D., Möller, T., ...
Using spectroscopic ellipsometry, we study the optical conductivity sigma(omega) of insulating LaSrMnO4 in the energy range of 0.75-5.8 eV from 15 to 330 K. The layered structure gives rise to a...
Burnus, T., Hu, Z., Hsieh, H. H., Joly, V. L. J., Joy, P. A., Haverkort, M. W., ...
We have studied the local electronic structure of LaMn0.5Co0.5O3 using soft-x-ray absorption spectroscopy at the Co-L_3,2 and Mn-L_3,2 edges. We found a high-spin Co^{2+}--Mn^{4+} valence state for...
Non-resonant inelastic x-ray scattering involving excitonic excitations (2007)
Haverkort, M. W., Tanaka, A., Tjeng, L. H., Sawatzky, G. A.
In a recent publication Larson \textit{et al.} reported remarkably clear $d$-$d$ excitations for NiO and CoO measured with x-ray energies well below the transition metal $K$ edge. In this letter we...
Burnus, T., Hu, Z., Haverkort, M. W., Cezar, J. C., Flahaut, D., Hardy, V., ...
We have investigated the valence, spin, and orbital state of the Co ions in the one-dimensional cobaltate Ca3Co2O6 using x-ray absorption and x-ray magnetic circular dichroism at the Co-L2,3 edges....
The spin state transition in LaCoO$_{3}$; revising a revision (2006)
Haverkort, M. W., Hu, Z., Cezar, J. C., Burnus, T., Hartmann, H., Reuther, M., ...
Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-$L_{2,3}$ edge we reveal that the spin state transition in LaCoO$_{3}$ can be well described by a low-spin ground...
Mott-Hubbard exciton in the optical conductivity of YTiO3 and SmTiO3 (2006)
Gössling, A., Schmitz, R., Roth, H., Haverkort, M. W., Lorenz, T., Mydosh, J. A., ...
In the Mott-Hubbard insulators YTiO3 and SmTiO3 we study optical excitations from the lower to the upper Hubbard band, d^1d^1 -> d^0d^2. The multi-peak structure observed in the optical conductivity...
Direct observation of t2g orbital ordering in magnetite (2006)
Schlappa, J., Schuessler-Langeheine, C., Chang, C. F., Ott, H., Tanaka, A., Hu, Z., ...
Using soft-x-ray diffraction at the site-specific resonances in the Fe L23 edge, we find clear evidence for orbital and charge ordering in magnetite below the Verwey transition. The spectra show...
Orbital-assisted metal-insulator transition in VO$_{2}$ (2005)
Haverkort, M. W., Hu, Z., Tanaka, A., Reichelt, W., Streltsov, S. V., Korotin, M. A., ...
We found direct experimental evidence for an orbital switching in the V 3d states across the metal-insulator transition in VO$_{2}$. We have used soft-x-ray absorption spectroscopy at the V $L_{2,3}$...
Podlesnyak, A., Streule, S., Mesot, J., Medarde, M., Pomjakushina, E., Conder, K., ...
A gradual spin-state transition occurs in LaCoO3 around T~80-120 K, whose detailed nature remains controversial. We studied this transition by means of inelastic neutron scattering (INS), and found...
The class of transition metal compounds shows an enormous richness of physical properties, such as metal-insulator transitions, colossal magneto-resistance, super-conductivity, magneto-optics and...
Controlling orbital moment and spin orientation in CoO layers by strain (2005)
Csiszar, S. I., Haverkort, M. W., Hu, Z., Tanaka, A., Hsieh, H. H., Lin, H. -J., ...
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 L$_{2,3}$...
Aligning spins in antiferromagnetic films using antiferromagnets (2005)
Csiszar, S. I., Haverkort, M. W., Burnus, T., Hu, Z., Tanaka, A., Hsieh, H. H., ...
We have explored the possibility to orient spins in antiferromagnetic thin films with low magnetocrystalline anisotropy via the exchange coupling to adjacent antiferromagnetic films with high...
Nature of magnetism in Ca$_3$Co$_2$O$_6$ (2005)
Wu, Hua, Haverkort, M. W., Hu, Z., Khomskii, D. I., Tjeng, L. H.
We find using LSDA+U band structure calculations that the novel one-dimensional cobaltate Ca$_3$Co$_2$O$_6$ is not a ferromagnetic half-metal but a Mott insulator. Both the octahedral and the...
Optical study of orbital excitations in transition-metal oxides (2005)
Rückamp, R., Benckiser, E., Haverkort, M. W., Roth, H., Lorenz, T., Freimuth, A., ...
The orbital excitations of a series of transition-metal compounds are studied by means of optical spectroscopy. Our aim was to identify signatures of collective orbital excitations by comparison with...
Zero-field incommensurate spin-Peierls phase with interchain frustration in TiOCl (2005)
Rückamp, R., Baier, J., Kriener, M., Haverkort, M. W., Lorenz, T., Uhrig, G. S., ...
We report on the magnetic, thermodynamic and optical properties of the quasi-one-dimensional quantum antiferromagnets TiOCl and TiOBr, which have been discussed as spin-Peierls compounds. The...
Different look at the spin state of Co3+ ions in a CoO5 pyramidal coordination (2004)
Hu,Z., Wu,H., Haverkort,M. W., Hsieh,H. H., Lin,H. J., Lorenz,T., ...
Determination of the orbital moment and crystal field splitting in LaTiO$_{3}$ (2004)
Haverkort, M. W., Hu, Z., Tanaka, A., Ghiringhelli, G., Roth, H., Cwik, M., ...
Utilizing a sum-rule in a spin-resolved photoelectron spectroscopic experiment with circularly polarized light, we show that the orbital moment in LaTiO$_3$ is strongly reduced both below and above...
Different look at the spin state of Co3+ ions in a CoO5 pyramidal coordination (2004)
Hu, Z., Wu, H., Haverkort, M. W., Hsieh, H. H., Lin, H. J., Lorenz, T., ...
Magnetic versus crystal field linear dichroism in NiO thin films (2003)
Haverkort, M. W., Csiszar, S. I., Hu, Z., Altieri, S., Tanaka, A., Hsieh, H. H., ...
We have detected strong dichroism in the Ni $L_{2,3}$ x-ray absorption spectra of monolayer NiO films. The dichroic signal appears to be very similar to the magnetic linear dichroism observed for...
A different look at the spin state of Co$^{3+}$ ions in CoO$_{5}$ pyramidal coordination (2003)
Hu, Z., Wu, Hua, Haverkort, M. W., Hsieh, H. H., Lin, H. -J., Lorenz, T., ...
Using soft-x-ray absorption spectroscopy at the Co-$L_{2,3}$ and O-$K$ edges, we demonstrate that the Co$^{3+}$ ions with the CoO$_{5}$ pyramidal coordination in the layered Sr$_2$CoO$_3$Cl compound...
Growth and properties of strained VOx thin films with controlled stoichiometry (2003)
Rata, A. D., Chezan, A. R., Hibma, T., Haverkort, M. W., Tjeng, L. H., Hsieh, H. H., ...
We have succeeded in growing epitaxial films of rocksalt VOx on MgO(001) substrates. The oxygen content as a function of oxygen flux was determined using 18O2-RBS and the vanadium valence using XAS....