A5021747342- Multiferroics and related materials
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- X-ray Diffraction in Crystallography
- Advanced NMR Techniques and Applications
- Physics of Superconductivity and Magnetism
- High-pressure geophysics and materials
- Rare-earth and actinide compounds
- Magnetic properties of thin films
- Superconducting Materials and Applications
- Ferroelectric and Piezoelectric Materials
- Crystallization and Solubility Studies
- Inorganic Fluorides and Related Compounds
- Crystal Structures and Properties
- Advanced MRI Techniques and Applications
- Iron-based superconductors research
- Magnetic Properties and Applications
- Magnetic Properties of Alloys
- Solid-state spectroscopy and crystallography
- Topological Materials and Phenomena
- Material Science and Thermodynamics
- Electronic and Structural Properties of Oxides
RWTH Aachen University
2015-2024
Technical University of Munich
2005-2023
Heinz Maier-Leibnitz Zentrum
2010-2023
Forschungszentrum Jülich
2014-2022
Grunberger Diabetes Institute
2021
Institute of Crystallography
2019-2021
Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute
2002-2007
Oak Ridge National Laboratory
2005
Argonne National Laboratory
2005
National Institute of Research and Development for Optoelectronics
1998-2000
Spin ices are exotic phases of matter characterized by frustrated spins obeying local ice rules, in analogy with the electric dipoles water ice. In two dimensions, one can similarly define rules for in-plane Ising-like arranged on a kagome lattice. These require each triangle plaquette to have single monopole, and lead various unique orders excitations. Using experimental theoretical approaches including magnetometry, thermodynamic measurements, neutron scattering Monte Carlo simulations, we...
An investigation of the low-temperature magnetism TmMgGaO${}_{4}$, a recently synthesized ``triangular-lattice Ising antiferromagnet,'' reveals an unconventional magnetic architecture that might arise in other similar rare-earth magnets.
The crystal structure of a new superconductor UTe 2 has been investigated using single-crystal neutron diffraction for the first time at low temperature (LT) 2.7 K, just above superconducting transition ∼1.6 in order to clarify whether orthorhombic type Immm (No. 71), reported room-temperature (RT) persists down phase and can be considered as parent symmetry development spin-triplet superconductivity. In contrast previously about 100 K [Stöwe (1996). J. Solid State Chem . 127 , 202–210], our...
Detailed structural investigation of Ba${}_{2}$CoGe${}_{2}$O${}_{7}$ was performed in its low-temperature multiferroic state combining neutron diffraction with magnetization measurements and the optical study lattice vibrations on single crystals. The crystal structure above (10.4 K) magnetic structures below (2.2 antiferromagnetic transition temperature ${T}_{N}$ $=$ 6.7 K were determined using diffraction. tetragonal space group (SG) $P$-42${}_{1}m$, corresponding to average at room...
POLI, which is operated by the Institute of Crystallography, RWTH Aachen University in cooperation with JCNS, Forschungszentrum Jülich, a versatile two axes single crystal diffractometer broad field applications. Mostly dedicated to investigation magnetic structures crystals using neutron spin polarisation, POLI also used for classical structural investigations under extreme conditions. High intensity hot neutrons flux makes it attractive other applications like study parity violations...
Crystal structure of Ba${}_{2}$CoGe${}_{2}$O${}_{7}$ at room temperature (RT) and 90 K has been probed by single-crystal diffraction x-ray synchrotron radiation. The space group (SG) found both temperatures is well approximated $P$-42${}_{1}m$, in agreement with expectation for melilite-like compounds. real more distorted a lower symmetry, as follows from observation set superstructure reflections violating 2${}_{1}$ symmetry. Symmetry analysis based on the observed average-structure SG...
We report on spherical neutron polarimetry and unpolarized diffraction in zero magnetic field as well flipping ratio static magnetization measurements high fields the multiferroic square lattice antiferromagnet ${\text{Ba}}_{2}{\text{CoGe}}_{2}{\text{O}}_{7}$. found that space group is $C{m}^{\ensuremath{'}}m{2}^{\ensuremath{'}}$ with sublattice parallel to [100] axis of this orthorhombic setting. The spin canting has been be smaller than $0.{2}^{\ensuremath{\circ}}$ ground state. This...
3D vector polarisation analysis called also SNP (Spherical Neutron Polarimetry) is a powerful method for the detailed investigation of complex magnetic structures. The precise control incoming and scattered neutron polarisations essential this technique. Here we show an instrumental setup, that was recently implemented on new single crystal diffractometer POLI-HEiDi at FRM II performing experiments using two 3He spin filters production polarisation. design optimisation procedure used filter...
We report a crystal growth method to obtain homochiral single crystals of ${\mathrm{CsCuCl}}_{3}$ and polarized neutron diffraction studies examine the chiral helimagnetism this compound. The were grown by two-step crystallization. First, millimeter-sized seed synthesized spontaneous crystallization with stirring. handedness was determined x-ray diffraction. Then, centimeter-sized obtained from selected crystals. large made it possible perform clarified strong correlation between magnetic...
A new polarized neutron single crystal diffractometer POLI (Polarization Investigator) has been developed at the Maier-Leibnitz Zentrum, Garching, Germany. After reviewing existing devices, spherical polarimetry implemented on as a main experimental technique using third-generation cryogenic polarization analysis device (Cryopad) built in cooperation between RWTH University and Institut Laue-Langevin. In this report we describe realization present performance of Cryopad POLI. Some...
Synthetic Co 2 SiO 4 crystallizes in the olivine structure (space group Pnma) with two crystallographically non-equivalent positions and shows antiferromagnetic ordering below 50 K. We have investigated temperature variation of magnetic by means non-polarized polarized neutron diffraction for single crystals. Measurements neutrons were made at 2.5 K (below T N ), whereas experiments carried out 70 150 (above ) an external field 7 parallel to b axis. Additional accurate powder studies...
We report a combined polarized and unpolarized neutron diffraction study on multiferroic ${\mathrm{Sr}}_{2}{\mathrm{CoSi}}_{2}{\mathrm{O}}_{7}$ (SCSO) single crystal below above the antiferromagnetic ordering temperature ${\mathrm{T}}_{N}$ = 6.5 K. Unpolarized measurements at 15 K confirm melilite-type tetragonal $P\overline{4}{2}_{1}m$ space group as parent structure of SCSO. The low 2.3 K, in contrast, reveals symmetry lowering with orthorhombic $Cm{m}^{\ensuremath{'}}{2}^{\ensuremath{'}}$...
Two aspects of the ambient pressure magnetic structure heavy fermion material CeRhIn5 have remained under some debate since its discovery: whether is indeed an incommensurate helix or a spin density wave, and what precise magnitude ordered moment. By using single crystal sample optimized for hot neutrons to minimize neutron absorption by Rh In, here we report moment . In addition, spherical polarimetry measurements on similar sample, confirmed helical nature structure, identified chiral domain.
The control of multiferroic domains through external electric fields has been studied by dielectric measurements and polarized neutron diffraction on single-crystalline TbMnO3. Full hysteresis cycles were recorded varying an field the order several kV mm−1 recording chiral magnetic scattering as well charge in a sample capacitor. Both methods yield comparable coercive that increase upon cooling.
$5d$ iridium oxides are of huge interest due to the potential for new quantum states driven by strong spin-orbit coupling. The strontium iridate Sr$_2$IrO$_4$ is particularly in spotlight because so-called $j_\text{eff}=1/2$ state consisting a superposition three local $t_{2g}$ orbitals with -- its most simple version nearly equal population, which stabilizes an unconventional Mott insulating state. Here, we report anisotropic and aspherical magnetization density distribution measured...
For a symmetry-consistent theoretical description of the multiferroic phase Ba 2 CoGe O 7 precise knowledge its crystal structure is prerequisite. In previous synchrotron X-ray diffraction experiment on at room temperature, forbidden reflections were found that favour tetragonal-to-orthorhombic symmetry lowering compound [Hutanu, Sazonov, Murakawa, Tokura, Náfrádi & Chernyshov (2011), Phys. Rev. B , 84 212101]. Here, results are reported room-temperature single-crystal studies with both...
Abstract Multiferroic Ba 2 CuGe O 7 was anticipated as a potential member of the exciting group materials hosting skyrmion or vortex lattice because its profound Dzyaloshinskii–Moriya interaction (DMI) and absence single ion anisotropy (SIA). This phase, however, could not be evidenced instead, it exhibits complex incommensurate antiferromagnetic (AFM) cycloidal structure. Its sister compound MnGe , in contrast, is characterized by relatively strong in-plane exchange that competes with...
Abstract HEiDi is one of the two single crystal diffractometers at neutron source Heinz Maier-Leibnitz (FRM II). The instrument placed beam tube SR9b in experimental hall. It was developed collaboration between RWTH Aachen (Institut für Kristallographie) and TU München II) to cover a broad range scientific cases area structural research on crystals.
Gaseous 3He neutron spin filters (NSF) are simple transmission devices, with predictable characteristics, that do not require any special optical adjustments on a beam. Since polarized nuclei of possess very high spin-dependent absorption efficiency over wide range energies, the NSF can be used as broadband polarizer or analyzer, possibility to optimize its for nearly all wavelengths. In 2005 facility large-scale production highly gas, HELIOS, was put into operation at FRM-II.
For a symmetry-consistent theoretical description of the ferroelectric phase Ba2MnGe2O7 melilite compound, precise knowledge its crystal structure is prerequisite. Here we report results single-crystal neutron diffraction experiments on at room (300 K) and low (10 temperatures. The structural model based tetragonal space group P4̅21 m describes symmetry both We found reflections forbidden in typical melilite-type structure. A comparison experimental data collected by means thermal cold...