A5088740151- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Magnetism in coordination complexes
- Magnetic and transport properties of perovskites and related materials
- Organic and Molecular Conductors Research
- Iron-based superconductors research
- Multiferroics and related materials
- Theoretical and Computational Physics
- Magnetic Properties of Alloys
- Magnetic properties of thin films
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Metal-Organic Frameworks: Synthesis and Applications
- Advanced NMR Techniques and Applications
- Ferroelectric and Piezoelectric Materials
- Quantum and electron transport phenomena
- Solid-state spectroscopy and crystallography
- Muon and positron interactions and applications
- Electron Spin Resonance Studies
- Boron and Carbon Nanomaterials Research
- Advanced Thermoelectric Materials and Devices
- Lanthanide and Transition Metal Complexes
- Quantum many-body systems
- Crystal Structures and Properties
Helmholtz-Zentrum Berlin für Materialien und Energie
2013-2025
Deutsches Elektronen-Synchrotron DESY
2010
Slovak Academy of Sciences
2010
Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute
2000-2009
German Orient Foundation
2000-2008
Technische Universität Braunschweig
1994-2005
Eastern Washington University
2004
McMaster University
1997-2000
Japan External Trade Organization
1998
ETH Zurich
1992-1997
Neutron powder diffraction and single crystal x-ray resonant magnetic scattering measurements suggest that Dy plays an active role in enhancing the ferroelectric polarization multiferroic ${\mathrm{DyMnO}}_{3}$ above ${T}_{N}^{\mathrm{Dy}}=6.5\text{ }\text{ }\mathrm{K}$. We observe evolution of incommensurate ordering moments with same periodicity as Mn spiral ordering. It closely tracks polarization. Below ${T}_{N}^{\mathrm{Dy}}$, where spins order commensurately, decreases to values...
Ferrimagnetic CoFe2O4 nanopillars embedded in a ferroelectric BaTiO3 matrix are an example for two-phase magnetoelectrically coupled system. They operate at room temperature and free of any resource-critical rare-earth element, which makes them interesting potential applications. Prior studies succeeded showing strain-mediated coupling between the two subsystems. In particular, electric properties can be tuned by magnetic fields fields. Here we take analysis to new level utilizing soft X-ray...
Single-crystal magnetic susceptibility and specific heat studies of the one-dimensional copper complex [PM·Cu(NO3)2·(H2O)2]n (PM = pyrimidine) show that it behaves like a uniform S 1/2 antiferromagnetic Heisenberg chain, characterized by exchange parameter J/kB 36 K. Specific measurements in applied field, however, reveal formation field-induced spin excitation gap, whose magnitude depends on direction field. This behaviour is inconsistent with ideal chain. In low-temperature region,...
The zero-field muon spin relaxation technique has been used in the direct observation of spontaneous magnetic order below a Curie temperature ( T c ) ∼16.1 kelvin fullerene charge-transfer salt (tetrakisdimethylaminoethylene)C 60 [(TDAE)C ]. Coherent ordering electronic moments leads to local field 68(1) gauss at site 3.2 (parentheses indicate error last digit). Substantial spatially inhomogeneous effects are manifested distribution fields, whose width amounts 48(2) same temperature....
We report muon spin rotation measurements on the antiferromagnetic heavy-fermion superconductor U${\mathrm{Pd}}_{2}$${\mathrm{Al}}_{3}$ in superconducting state. The London penetration depth is found to be approximately isotropic, ${\ensuremath{\lambda}}_{\ensuremath{\perp}}(0)=4800\ifmmode\pm\else\textpm\fi{}500$ \AA{} and ${\ensuremath{\lambda}}_{\ensuremath{\parallel}}(0)=4500\ifmmode\pm\else\textpm\fi{}500$ \AA{}. ${\ensuremath{\mu}}^{+}$ Knight shift behavior below ${T}_{c}$ indicates...
Combining polarized and unpolarized neutron scattering techniques with x-ray resonant magnetic we have studied the coupling between Mn- R-spin-ordering in multiferroic RMnO3, R = Tb Dy. Polarized diffraction reveals moment orientation associated various modes describing complex ordering observed TbMnO3, while high fields allows identification of origin (Mn versus Tb) modes. In this way identify significant Cx Fz contributions from arising moments to Mn cycloidal ordering. The studies give...
A zinc-based metal–organic framework Zn2(adb)2(dabco)·4.5 DMF (K) (DUT-30(Zn), DUT = Dresden University of Technology, adb 9,10-anthracene dibenzoate, dabco =1,4-diazabicyclo[2.2.2]octane, N,N-dimethylformamide) was synthesized using a solvothermal route. This MOF exhibits six crystallographic guest dependent phases. Two them were characterized via single crystal X-ray analysis. The as-synthesized phase K crystallizes in the orthorhombic space group Fmmm, with 9.6349(9), b 26.235(3), and c...
The effect of biaxial strain on the oxygen octahedra rotations in a LaVO${}_{3}$ thin film is investigated using synchrotron radiation. First, we find that adopts distorted orthorhombic structure under compressive stress induced by SrTiO${}_{3}$ substrate. Second, separate contribution to superstructure peaks arising from cation displacement and VO${}_{6}$ order quantify rotation angles. Finally, an original ${a}^{\ensuremath{-}}{a}^{+}{c}^{\ensuremath{-}}$ tilt system, which imposed These...
The magnetic excitation spectrum of copper pyrimidine dinitrate, a material containing S = 1 / 2 antiferromagnetic chains with alternating g tensor and the Dzyaloshinskii-Moriya interaction exhibiting field-induced spin gap, is probed using submillimeter wave electron resonance spectroscopy. Ten modes are resolved in low-temperature spectrum, their frequency-field diagram systematically studied fields up to 25 T. experimental data sufficiently detailed make very accurate comparison...
We report on diffraction measurements multiferroic ${\mathrm{TbMnO}}_{3}$ which demonstrate that the Tb- and Mn-magnetic orders are coupled below ferroelectric transition ${T}_{\mathrm{FE}}=28\text{ }\text{ }\mathrm{K}$. For $T<{T}_{\mathrm{FE}}$ magnetic propagation vectors ($\mathbit{\ensuremath{\tau}}$) for Tb Mn locked so ${\mathbit{\ensuremath{\tau}}}^{\mathrm{Tb}}={\mathbit{\ensuremath{\tau}}}^{\mathrm{Mn}}$, while ${T}_{\mathrm{N}}^{\mathrm{Tb}}=7\text{ }\mathrm{K}$ we find...
X-ray resonant magnetic scattering studies of rare-earth ordering were performed on perovskite manganites $R{\text{MnO}}_{3}(R=\text{Dy},\text{Gd})$ in an applied field. The data reveal that the field-induced threefold polarization enhancement for $\mathbf{H}\ensuremath{\parallel}a(H\ensuremath{\approx}20\text{ }\text{kOe})$ observed ${\text{DyMnO}}_{3}$ below 6.5 K is due to a re-emergence Mn-induced Dy spin order with propagation vector...
Using soft x-ray diffraction at the Dy-M₅ resonance, pronounced circular dichroism in ferroelectric phase of DyMnO₃ is observed connection with sizable b and c components Dy-4f magnetic moments. This provides strong evidence for cycloidal order 4f moments, corroborating that inversion-symmetry breaking this material not accomplished by Mn spins alone. The allows us to image multiferroic domains are imprinted on surface using local charging beam via photoelectric effect.
X-ray absorption spectroscopy measurements in Pr${}_{0.5}$Ca${}_{0.5}$CoO${}_{3}$ and (Pr,Y)${}_{0.55}$Ca${}_{0.45}$CoO${}_{3}$ compositions reveal that the valence of praseodymium ions is stable essentially $+$3 (Pr [4${f}^{2}$]) metallic state, but abruptly changes when carriers localize approaching oxidation state $+$4 [4${f}^{1}$]). This mechanism appears to be driving force metal-insulator transition. The ground insulating a homogeneous...
X-ray absorption spectroscopy measurements in Pr${}_{0.5}$Ca${}_{0.5}$CoO${}_{3}$ were performed at the Pr ${M}_{4,5}$, ${L}_{3}$, and Ca ${L}_{2,3}$ edges as a function of temperature below 300 K. spectra show no changes down to 10 K while noticeable thermally dependent evolution takes place across metal-insulator transition. Spectral are analyzed by different methods, including multiple scattering simulations, which provide quantitative details on an electron loss 4$f$ orbitals. We...
The intrinsic structural dynamic during the adsorption of CO2 at 195 K and N2 77 on flexible porous coordination polymer Zn2(BPnDC)2(bpy) (SNU-9) was studied in situ by powder XRD. crystal structures as made solvent free (activated) phases were determined single X-ray diffraction. During transformation caused activation, rearrangement Zn–O bonds occurs that leads to changes environment Zn atoms. Such lead contraction unit cell decreasing volume nearly 28% comparison pristine structure....
Synchrotron x-ray diffraction and resonant magnetic scattering experiments on a single crystal of orthorhombic ${\mathrm{DyMnO}}_{3}$ have been carried out between 4 $40\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Below ${T}_{N}^{\mathrm{Dy}}=5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the Dy moments order in commensurate structure with propagation vector $0.5\phantom{\rule{0.3em}{0ex}}{\mathbf{b}}^{*}$. Simultaneous ordering, an incommensurate lattice modulation...
We present a combined experimental and theoretical study of the mineral atacamite ${\mathrm{Cu}}_{2}\mathrm{Cl}(\mathrm{OH}{)}_{3}$. Density-functional theory yields Hamiltonian describing anisotropic sawtooth chains with weak 3D connections. Experimentally, we fully characterize antiferromagnetically ordered state. Magnetic order shows complex evolution magnetic field, while, starting at 31.5 T, observe plateaulike magnetization about ${M}_{\mathrm{sat}}/2$. Based on complementary...
<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>Ho</a:mi><a:mn>3</a:mn></a:msub><a:msub><a:mi>ScO</a:mi><a:mn>6</a:mn></a:msub></a:mrow></a:math> harbors a frustrated maple leaf lattice (MLL). It crystalizes in the <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:msub><b:mi>Mg</b:mi><b:mn>3</b:mn></b:msub><b:msub><b:mi>TeO</b:mi><b:mn>6</b:mn></b:msub></b:mrow></b:math>-type structure and has centrosymmetric trigonal space group (<c:math...
Temperature-dependent in situ continuous wave (cw) electron spin resonance (ESR) measurements are used for investigating changes magnetization upon reduction and reoxidation La-deficient La x Fe0.7Mn0.3O3 (x < 1) samples to advance the understanding of structural chemical these materials where A-site deficiency was shown affect catalytic performance. For defect-rich mixed perovskites with ferromagnetic ordering, magnetic properties as characterized by cw ESR spectroscopy sensitive probes...
We have employed soft and hard x-ray resonant magnetic scattering polarized neutron diffraction to study the interface bulk antiferromagnetic domain state of archetypal epitaxial ${\text{Ni}}_{81}{\text{Fe}}_{19}(111)/\text{CoO}(111)$ exchange biased bilayer. The combination these methods provides unprecedented detailed insights into still incomplete understanding some key manifestations bias effect. show that several orders magnitude difference between expected measured value field is...