A5018748015- Rare-earth and actinide compounds
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Nuclear Physics and Applications
- High-pressure geophysics and materials
- Magnetic Properties of Alloys
- Atomic and Subatomic Physics Research
- Transboundary Water Resource Management
- Chalcogenide Semiconductor Thin Films
- Semiconductor Quantum Structures and Devices
- Multiferroics and related materials
- Social Acceptance of Renewable Energy
- Magnetic properties of thin films
- Advanced Chemical Physics Studies
- Inorganic Chemistry and Materials
- Quantum Dots Synthesis And Properties
- Nuclear reactor physics and engineering
- Advanced NMR Techniques and Applications
- Corporate Taxation and Avoidance
- Metal and Thin Film Mechanics
- Geophysical Methods and Applications
- Health and Conflict Studies
- Advanced Semiconductor Detectors and Materials
Heinz Maier-Leibnitz Zentrum
2009-2023
Technical University of Munich
2010-2023
Universität Hamburg
2009-2017
TU Dresden
2008
Centre National de la Recherche Scientifique
1998-2002
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
1998-2002
Laboratoire Léon Brillouin
1998-2002
CEA Paris-Saclay
1998-2002
University of Göttingen
2000
University of Geneva
1994-1997
The magnetic excitations in multiferroic TbMnO3 have been studied by inelastic neutron scattering the spiral and sinusoidally ordered phases. At incommensurate zone center of phase, we find three low-lying magnons whose character has fully determined using neutron-polarization analysis. excitation at lowest energy is sliding mode spiral, two modes 1.1 2.5 meV correspond to rotations rotation plane. These latter are expected couple electric polarization. perfect agreement with recent...
We study the symmetry of spin excitation spectra in 122-ferropnictide superconductors by comparing results first-principles calculations with inelastic neutron-scattering (INS) measurements on ${\text{BaFe}}_{1.85}{\text{Co}}_{0.15}{\text{As}}_{2}$ and ${\text{BaFe}}_{1.91}{\text{Ni}}_{0.09}{\text{As}}_{2}$ samples that exhibit neither static magnetic phases nor structural phase transitions. In both normal superconducting (SC) states, spectrum lacks three-dimensional ${4}_{2}/m$ screw around...
Antiferromagnetic ordering and structural phase transition have been investigated via comprehensive neutron x-ray diffraction on Sn-flux-grown ${\text{BaFe}}_{2}{\text{As}}_{2}$ single crystals, the $A\text{\ensuremath{-}}122$ family of FeAs-based high-${T}_{C}$ superconductor compounds. The incorporation Sn in lattice resulted to an average composition ${\text{Ba}}_{0.95}{\text{Sn}}_{0.05}{\text{Fe}}_{2}{\text{As}}_{2}$. A tetragonal-to-orthorhombic a three-dimensional long-range...
Recent research has provided new insights into the relationship between climate change and violent conflict. In this review we compare results, methodologies, data applied in peer-reviewed literature to recap current state of debate. While long-term historical studies suggest a coincidence variability armed conflict, empirical findings are less conclusive for recent periods. Disentangling climate-conflict nexus, discuss causal pathways such as precipitation changes, freshwater scarcity, food...
A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within central volume 1 m × gradient less than 300 pT/m, achieved without any external stabilization or compensation, is described. This performance represents more hundredfold improvement the state art for two-layer magnetic shield provides an environment suitable next generation precision experiments in fundamental physics at low energies; particular, searches electric dipole moments systems tests...
Adequate fresh water availability is an important factor for human security in many parts of the world. In transboundary river basins, decreased supply due to local environmental change and global climate increased demand growing populations continued economic development can aggravate scarcity. Contrary claim that scarcity may result risk armed conflict, there no simple relationship between freshwater violent conflict. Other crucial factors need be taken into consideration also directly...
MnSi is a cubic compound with small magnetic anisotropy, which stabilizes helimagnetic spin spiral that reduces to ferromagnetic and antiferromagnetic state in the long- short-wavelength limits, respectively. We report comprehensive inelastic neutron-scattering study of collective excitations MnSi. In our we observe rich variety seemingly anomalous excitation spectra, as measured well over 20 different locations reciprocal space. Using model based on only three parameters, namely, pitch...
The magnetic excitations in multiferroic TbMnO3 have been investigated by inelastic scattering of polarized and unpolarized neutrons the ferroelectric cycloidal paraelectric collinear phase. polarization analysis at incommensurate zone center allows one to determine characters three distinct modes. In particular we may identify those modes which directly couple polarization. We find a rather complex magnon dispersion with branches split throughout Brillouin zone, should be generic...
We present an experimental study of the two-dimensional $S=\frac{1}{2}$ square-lattice antiferromagnet $\text{Cu}{(\text{pz})}_{2}{({\text{ClO}}_{4})}_{2}$ (pz denotes pyrazine-${\text{C}}_{4}{\text{H}}_{4}{\text{N}}_{2}$) using specific-heat measurements, neutron diffraction, and cold-neutron spectroscopy. The magnetic field dependence ordering temperature was determined from measurements for fields perpendicular parallel to planes, showing identical field-temperature phase diagrams. This...
Inelastic neutron-scattering experiments on the high-temperature superconductor ${\mathrm{La}}_{1.855}{\mathrm{Sr}}_{0.145}{\mathrm{CuO}}_{4}$ reveal a magnetic excitation gap $\ensuremath{\Delta}$ that decreases continuously upon application of field perpendicular to ${\mathrm{CuO}}_{2}$ planes. The vanishes at critical required induce long-range incommensurate antiferromagnetic order, providing compelling evidence for field-induced soft-mode driven quantum phase transition.
The intriguing phase transition discovered recently in TmTe at ${T}_{Q}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{K}$ is characterized as antiferroquadrupolar by neutron diffraction. In an applied magnetic field, the underlying ordered structure of Tm quadrupole moments disclosed appearance antiferromagnetic component dipole moments. This induced described wave vector $\mathit{k}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(1/2,1/2,1/2)$ for...
We have studied the two-dimensional S=1/2 square-lattice antiferromagnet Cu(pz)_{2}(ClO4)_{2} (where pz denotes pyrazine), using neutron inelastic scattering and series expansion calculations. show that presence of antiferromagnetic next-nearest-neighbor interactions enhances quantum fluctuations associated with resonating valence bonds. Intermediate magnetic fields lead to a selective tuning bonds spectacular inversion zone-boundary dispersion, providing novel insight into 2D...
Low-temperature resistance measurements were performed on UTe crystals in the pressure range from 1 GPa to 20 GPa. The Curie temperature obtained as maximum derivative dR/dT, increases strongly with pressure. It has a at 7.5 followed by decrease smaller slope higher pressures. Another anomaly R-T characteristic is observed above 10 and ascribed presence of B2 phase, which known form very sluggish phase transformation.
Precursor phenomena were investigated in a Ni-Fe-Ga alloy close to the stoichiometric Heusler composition ${\text{Ni}}_{2}\text{FeGa}$. In particular, phonon-dispersion curves, diffuse scattering and magnetic properties of single crystalline ${\text{Ni}}_{51.5}{\text{Fe}}_{21.5}{\text{Ga}}_{27}$ measured as function temperature. The ${\text{TA}}_{2}$ branch along [110] direction $\text{L}{2}_{1}$ phase shows significant phonon softening around $\ensuremath{\xi}=0.35$ resulting marked dip...
We use cold neutron spectroscopy to study the low-energy spin excitations of superconducting (SC) FeSe0.4Te0.6 and essentially nonsuperconducting (NSC) FeSe0.45Te0.55. In contrast with BaFe2-x(Co,Ni)xAs2, where are commensurate both in SC normal state, normal-state incommensurate show an hourglass dispersion near resonance energy. Since similar is also found NSC FeSe0.45Te0.55, we argue that observed FeSe(1-x)Tex not directly associated superconductivity. Instead, results can be understood...
The field-induced multiferroic transition in ${\text{TbMnO}}_{3}$ has been studied by neutron scattering. Apart from strong hysteresis, the magnetic associated with flop of electronic polarization exhibits a memory effect: after field sweep, does not exhibit same phase as that obtained zero-field cooling. changes excitations across perfectly agree rotation cycloidal spiral plane, indicating inverse Dzyaloshinski--Moriya coupling causes giant magnetoelectric effect at transition. analysis...
By inelastic neutron scattering, we have analyzed the magnetic correlations in paramagnetic metallic region of series Ca${}_{2\ensuremath{-}x}$Sr${}_{x}$RuO${}_{4}$, $0.2\ensuremath{\leqslant}x\ensuremath{\leqslant}0.62$. We find different contributions that correspond to two-dimensional ferromagnetic fluctuations and at incommensurate wave vectors ${Q}_{1}^{\mathrm{IC}}=(0.11,0,0)$, ${Q}_{2}^{\mathrm{IC}}=(0.26,0,0)$, ${Q}_{\ensuremath{\alpha}\ensuremath{\beta}}^{\mathrm{IC}}=(0.3,0.3,0)$....
We present high-resolution triple-axis neutron scattering studies of the high-temperature superconductor La${}_{1.88}$Sr${}_{0.12}$CuO${}_{4}$ (${T}_{c}=27$ K). The temperature dependence low-energy incommensurate magnetic fluctuations reveals distinctly glassy features. glassiness is confirmed by difference between ordering ${T}_{N}\ensuremath{\simeq}{T}_{c}$ inferred from elastic and freezing ${T}_{f}\ensuremath{\simeq}11$ K obtained muon spin rotation studies. field independence observed...
The temperature dependence of the gapped triplet excitations (triplons) in 2D Shastry-Sutherland quantum magnet SrCu$_2$(BO$_3$)$_2$ is studied by means inelastic neutron scattering. excitation amplitude rapidly decreases as a function while integrated spectral weight can be explained an isolated dimer model up to 10~K. Analyzing this anomalous line-shape terms damped harmonic oscillators shows that observed damping due two-component process: one component remains sharp and resolution...