A5075042296- Rare-earth and actinide compounds
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- Inorganic Chemistry and Materials
- Magnetic Properties of Alloys
- Physics of Superconductivity and Magnetism
- Fluid Dynamics and Heat Transfer
- Surface Modification and Superhydrophobicity
- High-pressure geophysics and materials
- Nanomaterials and Printing Technologies
- Magnetic and transport properties of perovskites and related materials
- Electrohydrodynamics and Fluid Dynamics
- Magnetic Properties and Synthesis of Ferrites
- Lattice Boltzmann Simulation Studies
- Multiferroics and related materials
- Proteins in Food Systems
- Contact Dermatitis and Allergies
- X-ray Diffraction in Crystallography
- Soft Robotics and Applications
- Nuclear Materials and Properties
- Agricultural Economics and Policy
- Medical Practices and Rehabilitation
- Pickering emulsions and particle stabilization
- Surface Roughness and Optical Measurements
- X-ray Spectroscopy and Fluorescence Analysis
University of Cologne
2009-2023
Significance The ground state of materials with strong electronic correlations depends on a delicate balance among competing interactions. strongly correlated compounds Ce M In 5 , = Co, Rh, and Ir, exhibit superconducting magnetic states as well Fermi surface changes upon substituting one element for another become even higher temperature superconductors when is substituted by Pu. They are therefore recognized important model systems in which search parameters correlating the occurrence...
Linear polarized soft-x ray absorption (XAS) and inelastic neutron scattering (INS) experiments have been performed on CeMIn5 with M = Rh, Ir, Co to determine the crystal-field scheme characteristic Kondo temperatures T* for hybridization between 4f conduction electrons. The ground state wave functions are determined from polarization dependent soft-XAS data at cerium M4,5 edge splittings INS. temperature has line widths of data. We find that quasielastic superconducting compounds CeCoIn5...
We have succeeded in establishing the crystal-field ground state of CeRu${}_{2}$Al${}_{10}$, an orthorhombic intermetallic compound recently identified as a Kondo insulator. Using polarization-dependent soft x-ray absorption spectroscopy at Ce ${M}_{4,5}$ edges, together with input from inelastic neutron and magnetic susceptibility experiments, we were able to determine unambiguously orbital occupation $4f$ shell explain quantitatively both measured moment along easy $a$ axis small ordered...
Soft x-ray absorption experiments on the transition metal L2,3 edge of multiferroic MnWO4 and antiferromagnetic CoWO4 are presented. The observed linear polarization dependence, analyzed by full-multiplet calculations, is used to determine ground state wave function magnetic Mn2+ Co2+ ions. impact local structure spin-orbit coupling orbital moment discussed in terms single-ion anisotropy. It shown that responsible for collinear antiferromagnetism, while small size effects make spiral order...
We have determined the ground-state wave functions and crystal-field-level schemes of CeRh${}_{2}$Si${}_{2}$ CeRu${}_{2}$Si${}_{2}$ using linear polarized soft x-ray-absorption spectroscopy (XAS) inelastic neutron scattering. find large crystal-field splittings which are made mainly ${J}_{z}$ = $|\ifmmode\pm\else\textpm\fi{}5/2\ensuremath{\rangle}$ with some amount $|\ensuremath{\mp}3/2\ensuremath{\rangle}$ in both compounds. The $4{f}^{0}$ contribution to ground state several members...
Experiments show that lattice relaxations play a role in the gradual spin-state and insulator-to-metal transitions of LaCoO${}_{3}$. The findings call for reconsideration transition energetics this related materials.
We have successfully determined the hitherto unknown sign of ${B}_{4}^{4}$ Stevens crystal-field parameter tetragonal heavy-fermion compound ${\mathrm{CeCu}}_{2}{\mathrm{Si}}_{2}$ using vector $\stackrel{^}{\mathbf{q}}$-dependent nonresonant inelastic x-ray scattering experiments at cerium ${N}_{4,5}$ edge. The observed difference between two different directions, $\stackrel{^}{\mathbf{q}}\ensuremath{\parallel}[100]$ and $\stackrel{^}{\mathbf{q}}\ensuremath{\parallel}[110]$, is due to...
Topological insulators form a novel state of matter that provides new opportunities to create unique quantum phenomena. While the materials used so far are based on semiconductors, recent theoretical studies predict also strongly correlated systems can show non-trivial topological properties, thereby allowing even emergence surface phenomena not possible with band insulators. From practical point view, it is expected strong correlations will reduce disturbing impact defects or impurities,...
CaBaFe${}_{4}$O${}_{7}$ is a mixed-valent transition metal oxide having both Fe${}^{2+}$ and Fe${}^{3+}$ ions in tetrahedral coordination. Here we characterize its magnetic properties by magnetization measurements investigate local electronic structure using soft x-ray absorption spectroscopy at the Fe ${L}_{2,3}$ edges, combination with multiplet cluster simulations band calculations. We found that ion unusual coordination Jahn-Teller active high-spin...
Here we present linear-polarization-dependent soft x-ray absorption spectroscopy data at the Ce ${M}_{4,5}$ edges of CeOs${}_{2}$Al${}_{10}$ and CeFe${}_{2}$Al${}_{10}$. Despite strong hybridization between $4f$ conduction electrons existence spin gaps as seen in inelastic neutron scattering, were able to determine crystal field ground state wave functions by combining our with magnetization measurements. The results quantitatively explain small ordered moment along $c$ measured magnetic...
We investigated the electronic structure of enigmatic CeRh$_3$B$_2$ using resonant inelastic scattering and x-ray absorption spectroscopy in combination with $ab$ $initio$ density functional calculations. find that Rh 4$d$ states are irrelevant for high-temperature ferromagnetism Kondo effect. also Ce 4$f$ crystal-field strength is too small to explain strong reduction magnetic moment. The data reveal instead presence two different active orbitals, each coupling selectively bands...
We present bulk-sensitive hard x-ray photoelectron spectroscopy (HAXPES) data of the Ce3d core levels and lifetime-reduced L edge absorption (XAS) in partial fluorescence yield (PFY) mode CeMIn5 family with M = Co, Rh, Ir. The HAXPES are analyzed quantitatively a combination full multiplet configuration interaction model which allows correcting for strong plasmons data, reliable weights wn different fn contributions ground state determined. results compared to other heavy fermion compounds...
This study represents an experimental investigation, complemented with a mathematical model, to decipher the effect of gravity on spreading dynamics water droplet. For theoretical discussion, overall energy balance approach is adopted explain droplet under both microgravity (μg) and terrestrial condition. Besides explaining mechanism condition achieved during parabolic flight, technique detailed set-up has also been developed for successful deposition A rational understanding formulated...
We determined the crystal-field split Hund's rule ground state of non-centrosymmetric heavy fermion superconductor CePt3Si with polarization dependent soft X-ray absorption spectroscopy (XAS) and polarized neutron scattering. are also able to give sequence states from temperature evolution linear dichroic signal in XAS. The quantitative analysis XAS dependence together transition energies complete identification level scheme.
The crystal-field ground state wave function of CeCu$_2$Si$_2$ has been investigated with linear polarized $M$-edge x-ray absorption spectroscopy from 250mK to 250K, thus covering the superconducting ($T_{\text{c}}$=0.6K), Kondo ($T_{\text{K}}$$\approx$20K) as well Curie-Weiss regime. comparison full-multiplet calculations shows that temperature dependence experimental dichroism is explained a $\Gamma_7^{(1)}$ ground-state and thermal population excited states at around 30meV. scheme does...
We have been able to induce a linear dichroic signal in the Yb M(5) x-ray absorption white line of cubic YbInNi(4) by application magnetic field. The nonzero integrated intensity field induced spectrum indicates net noncubic 4f orbital polarization. A quantitative analysis temperature and strength dependence establishes that crystal-field ground state is Γ(8) quartet. results demonstrate potential dichroism as new powerful approach for investigation degeneracy degrees freedom heavy-fermion...
We studied the ($00\frac{1}{2}$) diffraction peak in low-temperature phase of magnetite (${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$) using resonant soft x-ray at $\mathrm{Fe}\ensuremath{-}{L}_{2,3}$ and $\mathrm{O}\ensuremath{-}K$ resonances. both molecular-beam-epitaxy grown thin films situ cleaved single crystals. From comparison, we have been able to determine quantitatively contribution intrinsic absorption effects, thereby arriving a consistent result for spectrum. Our data also allow...
The magnetic form factor of YbInNi${}_{4}$ has been determined via the flipping ratios $R$ with polarized neutron diffraction, and scattering function $S(Q,\ensuremath{\omega})$ was measured in an inelastic experiment. Both experiments were performed aim determining crystal-field scheme. clearly excludes possibility a ${\ensuremath{\Gamma}}_{7}$ doublet as ground state. data exhibit two almost equally strong peaks at 3.2 meV 4.4 which points, agreement earlier data, toward...