A5060296216- Rare-earth and actinide compounds
- Iron-based superconductors research
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Magnetic Properties of Alloys
- Magnetic properties of thin films
- Multiferroics and related materials
- Corporate Taxation and Avoidance
- High-pressure geophysics and materials
- Inorganic Chemistry and Materials
- Nuclear physics research studies
- Boron and Carbon Nanomaterials Research
- Superconductivity in MgB2 and Alloys
- Crystal Structures and Properties
- Advanced Materials Characterization Techniques
- Magnetic Properties and Applications
- Cold Atom Physics and Bose-Einstein Condensates
Technische Universität Dresden
2015-2025
University of Birmingham
2010-2025
Leibniz Institute for Solid State and Materials Research
2023
Cerium hexaboride is a cubic f-electron heavy-fermion compound that displays rich array of low-temperature magnetic ordering phenomena which have been the subject investigation for more than 50 years. Its complex behaviour result competing interactions, with both itinerant and local electrons playing important roles. Investigating this material has proven to be substantial challenge, in particular because appearance 'magnetically hidden order' phase, remained elusive neutron-scattering...
We report superconducting (SC) properties of stoichiometric LiFeAs (Tc = 17 K) studied by small-angle neutron scattering (SANS) and angle-resolved photoemission (ARPES). Although the vortex lattice exhibits no long-range order, well-defined SANS rocking curves indicate better ordering than in chemically doped 122-compounds. The London penetration depth 210 nm, determined from magnetic field dependence form factor, is compared to that calculated ARPES band structure with adjustable...
Understanding the mechanism and symmetry of electron pairing in iron-based superconductors represents an important challenge condensed matter physics [1-3]. The observation magnetic flux lines - "vortices" a superconductor can contribute to this issue, because spatial variation field reflects pairing. Unlike many other iron pnictides, our KFe2As2 crystals have very weak vortex pinning, allowing small-angle-neutron-scattering (SANS) observations intrinsic lattice (VL). We observe nearly...
Abstract Complex low-temperature-ordered states in chiral magnets are typically governed by a competition between multiple magnetic interactions. The chiral-lattice multiferroic Cu 2 OSeO 3 became the first insulating helimagnetic material which long-range order of topologically stable spin vortices known as skyrmions was established. Here we employ state-of-the-art inelastic neutron scattering to comprehend full three-dimensional spin-excitation spectrum over broad range energies. Distinct...
We report on neutron scattering measurements the vortex lattice of noncentrosymmetric superconductor BiPd. observe existence intermediate mixed state, a region where Meissner and phases coexist, which is feature low <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>κ</a:mi></a:math> type-II superconductors. Following this, we obtain an estimate value <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mi>κ</b:mi></b:math> using extended London model. Finally, find that...
Low-energy spin excitations in any long-range ordered magnetic system the absence of magnetocrystalline anisotropy are gapless Goldstone modes emanating from ordering wave vectors. In helimagnets, these hybridize into so-called helimagnon excitations. Here we employ neutron spectroscopy supported by theoretical calculations to investigate excitation spectrum isotropic Heisenberg helimagnet ZnCr2Se4 with a cubic spinel structure, which spin-3/2 Cr3+ ions arranged geometrically frustrated...
Magnetic frustration in a material may drive spin-spiral order, spontaneously breaking the translation and chiral symmetries of crystal. The underlying hierarchy magnetic interactions is reflected magnon excitations, which can be probed by inelastic neutron scattering. Here, authors study dispersions magnons helimagnet FeP compare experimentally observed spectra with simulations. Upon examination alternative models, are able to correctly describe spin excitations unveil corresponding mechanism.
For the last few decades, researchers have been intrigued by multipolar ordering phenomena while looking for related quantum criticality in heavy-fermion Kondo system Ce$_{1-x}$La$_{x}$B$_6$. However, critical induced substitution level ($x$), temperature ($T$), and magnetic field ($B$) are poorly understood despite a large collection of experimental results is available. In this work, we present $T$-$B$, $x$-$T$, $x$-$B$ phase diagrams Ce$_{1-x}$La$_x$B$_6$ ($\mathbf{B}\parallel[110]$)....
While magnetic skyrmions have been explored in various materials, their antipodes known as antiskyrmions experimentally observed only recently very thin samples of the tetragonal ferromagnet Mn${}_{1.4}$PtSn. Here, authors present an experimental study on bulk single crystals Mn${}_{1.4}$PtSn by means neutron scattering and force microscopy. The results indicate that are not stable samples. Instead, texture takes form unusual fractal pattern domains with a characteristic length scale about...
In contrast to magnetic order formed by electrons' dipolar moments, ordering phenomena associated with higher-order multipoles (quadrupoles, octupoles, etc.) are more difficult characterize because of the limited choice experimental probes that can distinguish different multipolar moments. The heavy-fermion compound CeB6 and its La-diluted alloys among best-studied realizations long-range-ordered phases, often referred as "hidden order." Previously, hidden in phase II was identified primary...
We have observed a magnetic vortex lattice (VL) in BaFe2(As_{0.67}P_{0.33})2 (BFAP) single crystals by small-angle neutron scattering (SANS). With the field along c-axis, nearly isotropic hexagonal VL was formed range from 1 to 16 T, which is record for this technique pnictides, and no symmetry changes were observed. The temperature-dependence of signal measured confirms presence (non d-wave) nodes superconducting gap structure measurements at 5 T below. nodal effects suppressed high fields....
Among heavy-fermion metals, ${\mathrm{Ce}}_{3}{\mathrm{Pd}}_{20}{\mathrm{Si}}_{6}$ is one of the heaviest-electron systems known to date. Here we used high-resolution neutron spectroscopy observe low-energy magnetic scattering from a single crystal this compound in paramagnetic state. We investigated its temperature dependence and distribution momentum space, which was not accessible earlier measurements on polycrystalline samples. At low temperatures, quasielastic response with half-width...
We observe a hysteretic reorientation of the magnetic vortex lattice in noncentrosymmetric superconductor ${\mathrm{Ru}}_{7}{\mathrm{B}}_{3}$, with change orientation driven by altering field below ${T}_{\mathrm{c}}$. Normally chooses either single or degenerate set orientations respect to crystal at any given temperature, behavior well described prevailing phenomenological and microscopic theories. Here, absence typical VL structural transition, we continuous rotation which exhibits...
In zero magnetic field, the famous neutron spin resonance in f-electron superconductor CeCoIn5 is similar to recently discovered exciton peak non-superconducting CeB6. Magnetic field splits into two components, indicating that it a doublet. Here we employ inelastic scattering (INS) scrutinize dependence of fluctuations The shows markedly different behavior without any splitting. Instead, observe second field-induced magnon whose energy increases with field. At ferromagnetic zone center,...
The clathrate compound ${\mathrm{Ce}}_{3}{\mathrm{Pd}}_{20}{\mathrm{Si}}_{6}$ is a heavy-fermion metal that exhibits magnetically hidden order at low temperatures. Reputedly, this exotic type of magnetic ground state, known as ``phase II'', could be associated with the ordering Ce $4f$ quadrupolar moments. In contrast to conventional (dipolar) order, it has vanishing Bragg intensity in zero field and, result, escaped direct observation by neutron scattering until now. Here we report diffuse...
We performed small-angle neutron scattering (SANS) measurements on the helimagnetic spinel compound ZnCr2Se4. The ground state of this material is a multi-domain spin-spiral phase, which undergoes domain selection in magnetic field and reportedly exhibits transition to proposed spin-nematic phase at higher fields. observed continuous change structure as function temperature, well weak discontinuous jump spiral pitch across domain-selection upon increasing field. From our SANS results we have...
Using small angle neutron scattering, the anisotropy of magnetic vortex lattice (VL), in heavily hole-doped pnictide superconductor ${\text{KFe}}_{2}{\text{As}}_{2}$, was studied. Well-ordered VL scattering patterns were measured with fields applied directions between $\mathbf{B}\ensuremath{\parallel}\mathbf{c}$ and basal plane, rotating either towards $[100]$ or $[110]$. Slightly distorted hexagonal observed when $\mathbf{B}\ensuremath{\parallel}\mathbf{c}$. However, pattern more strongly...
We report on small-angle neutron scattering (SANS) measurements of the vortex lattice (VL) in twin-free $\mathrm{YBa}{}_{2}\mathrm{Cu}{}_{3}\mathrm{O}{}_{7}$, extending previously investigated maximum magnetic field 11 T up to 16.7 with applied parallel c axis. This is a microscopic study matter this region superconducting phase. find that high VL displays rhombic structure, field-dependent coordination passes through square configuration no lock-in field-independent structure. The pinning...
The cubic chiral helimagnets with the $P2_13$ space group represent a of compounds in which stable skyrmion-lattice state is experimentally observed. key parameter that controls energy landscape such systems and determines emergence topologically nontrivial magnetic structures Dzyaloshinskii-Moriya interaction (DMI). Chemical substitution recognized as convenient instrument to tune DMI real materials has been successfully utilized studies number magnets, MnSi, FeGe, MnGe, others. In our...
We report a study of the basal-plane anisotropy superfluid density in underdoped YBa$_{2}$Cu$_{4}$O$_{8}$ (Y124), showing effects both CuO$_{2}$ planes and fully occupied CuO chains. From small-angle neutron scattering measurements vortex lattice, we can infer superconducting (SC) properties for temperature ($T$) range $T=$ 1.5 K to $T_{\rm c}$ magnetic induction $B$ from 0.1 6 T. find that along \textbf{a} has simple $d$-wave T-dependence. However, \textbf{b} (the chain direction) falls...
One of the key effects which is predicted to arise in superconductors without a centre inversion mixing singlet and triplet order parameters, are no longer good quantum numbers on their own due parity. We have probed gap structure noncentrosymmetric superconductor Ru$_7$B$_3$, through small-angle neutron diffraction from vortex lattice, search for proposed mixed parameter. find that measured temperature dependence vortex-lattice form factor well characterised by model constructed describe...
We present a comprehensive investigation of lattice dynamics in the double-helix antiferromagnet FeP by means high-resolution time-of-flight neutron spectroscopy and ab initio calculations. Phonons can hybridize with magnetic excitations noncollinear magnets to significantly influence their properties. observed rich spectrum phonon excitations, which extends up ∼50 meV. performed detailed analysis calculated spectra for all high-symmetry points directions Brillouin zone. show that DFT...
The noncentrosymmetric superconductor Ru7B3has in previous studies demonstrated remarkably unusual behaviour its vortex lattice (VL), where the nearest neighbour directions of vortices dissociate from crystal and instead show a complex field-history dependence, VL rotates as field is changed. In this study, we look at form factor Ru7B3during to check for deviations established models, such London model. We find that data well described by anisotropic model, which accordance with theoretical...