A5021848565- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Advanced Condensed Matter Physics
- Organic and Molecular Conductors Research
- Physics of Superconductivity and Magnetism
- Magnetism in coordination complexes
- Magnetic and transport properties of perovskites and related materials
- High-pressure geophysics and materials
- Multiferroics and related materials
- Solid-state spectroscopy and crystallography
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Electronic and Structural Properties of Oxides
- Crystallography and molecular interactions
- Inorganic Fluorides and Related Compounds
- Perovskite Materials and Applications
- Synthesis and properties of polymers
- Topological Materials and Phenomena
- Mechanical and Optical Resonators
- Magnetic Properties of Alloys
- Zeolite Catalysis and Synthesis
- Iron oxide chemistry and applications
- Electromagnetic wave absorption materials
- Crystal Structures and Properties
- Inorganic Chemistry and Materials
Indian Institute of Technology Tirupati
2017-2024
University of Augsburg
2015-2022
Georgia Institute of Technology
2019
University of Bayreuth
2019
Augsburg University
2018-2019
Goethe University Frankfurt
2009-2018
Indian Institute of Technology Bombay
2006
Topological protection offers unprecedented opportunities for wave manipulation and energy transport in various fields of physics, including elasticity, acoustics, quantum mechanics electromagnetism. Distinct classes topological waves have been investigated by establishing analogues with the quantum, spin valley Hall effects. We here propose experimentally demonstrate possibility supporting multiple modes within a single platform. Starting from patterned elastic plate featuring double Dirac...
The spin-liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3 has been studied by measuring the uniaxial expansion coefficients alpha(i), specific heat, and magnetic susceptibility. Special emphasis was placed on mysterious anomaly around 6 K--a potential instability. Distinct strongly anisotropic lattice effects have observed at K, clearly identifying this feature as a second-order phase transition. Owing to large anomalies in application of Grüneisen scaling enabled us determine corresponding heat...
In this work we explore the overall structural behaviour of [(CH3)2NH2][Mn(HCOO)3] multiferroic compound across temperature range where its ferroelectric transition takes place by means calorimetry, thermal expansion measurements and variable powder single crystal X-ray diffraction. The results clearly prove presence a phase at Tt ~ 187 K (the which dielectric occurs) that involves symmetry change from Rc to Cc, twinning crystals, discontinuous variation unit cell parameters volume, sharp...
Temperature-pressure phase diagram of the Kitaev hyperhoneycomb iridate $\beta$-Li$_2$IrO$_3$ is explored using magnetization, thermal expansion, magnetostriction, and muon spin rotation ($\mu$SR) measurements, as well single-crystal x-ray diffraction under pressure ab initio calculations. The Neel temperature increases with slope 0.9 K/GPa upon initial compression, but reduction in polarization field $H_c$ reflects a growing instability incommensurate order. At 1.4 GPa, ordered state breaks...
We investigate the effect that temperature dependence of crystal structure a two-dimensional organic charge-transfer salt has on low-energy Hamiltonian representation electronic structure. For that, we determine $\ensuremath{\kappa}$-(BEDT-TTF)${}_{2}$Cu${}_{2}$(CN)${}_{3}$ for series temperatures between $T=5$ and 300 K by single X-ray diffraction analyze evolution with using density functional theory tight binding methods. find considerable corresponding triangular lattice Hubbard...
The coupling of the critical electronic system to a compressible lattice is found drastically alter Mott criticality.
A Verwey-type charge-ordering transition in magnetite at 120 K leads to the formation of linear units three iron ions with one shared electron, called trimerons. The recently-discovered pentoxide (Fe4O5) comprising mixed-valent cations octahedral chains, demonstrates another unusual 150 involving competing trimerons and dimerons. Here, we experimentally show that applied pressure can tune pattern Fe4O5 strongly affect ordering temperature. We report two charge-ordered phases, first which may...
The coupling of magnetic and electronic degrees freedom to the crystal lattice in ferromagnetic semimetal ${\mathrm{EuB}}_{6}$, which exhibits a complex order colossal magnetoresistance effect, is studied by high-resolution thermal expansion magnetostriction experiments. ${\mathrm{EuB}}_{6}$ may be viewed as model system, where pure magnetism-tuned transport response can comparatively simple environment, i.e., not influenced strong crystal-electric field effects Jahn-Teller distortions. We...
We present results of ultrasonic measurements on a single crystal the distorted diamond-chain compound azurite ${\mathrm{Cu}}_{3}$(${\mathrm{CO}}_{3}$)${}_{2}$(OH)${}_{2}$. Pronounced elastic anomalies are observed in temperature dependence longitudinal mode ${c}_{22}$ which can be assigned to relevant magnetic interactions system and their couplings lattice degrees freedom. From semiquantitative analysis contribution magnetoelastic coupling...
We report on the realization of a capacitive dilatometer, designed for high-resolution measurements length changes material temperatures 1.4 K ⩽ T 300 and hydrostatic pressure P 250 MPa. Helium (4He) is used as pressure-transmitting medium, ensuring hydrostatic-pressure conditions. Special emphasis has been given to guarantee, good approximation, constant-pressure conditions during temperature sweeps. The performance dilatometer demonstrated by coefficient thermal expansion at pressures ≃...
The quasi-two-dimensional organic charge-transfer salt κ -(BEDT-TTF) 2 Cu (CN) 3 is one of the prime candidates for a quantum spin-liquid due strong spin frustration its anisotropic triangular lattice in combination with proximity to Mott transition. Despite intensive investigations material’s low-temperature properties, several important questions remain be answered. Particularly puzzling are 6 K anomaly and enigmatic effects observed magnetic fields. Here we report on measurements which...
Powder X-ray diffraction (PXRD) and single-crystal neutron scattering were used to study in detail the structural properties of Cs2CuCl(4-x)Br(x) series, good realizations layered triangular antiferromagnets. Detailed temperature-dependent PXRD reveal a pronounced anisotropy thermal expansion for three different crystal directions orthorhombic structure without any phase transition down 20 K. Remarkably, varies $x$, leading distinct changes geometry local Cu environment as function...
High-pressure single-crystal X-ray diffraction at ambient temperature and high-pressure SQUID measurements down to 2 K were performed up ∼2.5 GPa on ammonium metal formates, [NH4][M(HCOO)3] where M = Mn2+, Fe2+, Ni2+, in order correlate structural variations magnetic behaviour. Similar distortions phase transitions observed for all compounds, although the transition pressures varied with size of cation. The antiferromagnetic ordering compounds was maintained as a function pressure, changed...
A systematic study using neutron diffraction and magnetic susceptibility are reported on Mn substituted ferrimagnetic inverse spinel Ti$_{1-x}$Mn$_{x}$Co$_2$O$_4$ in the temperature interval 1.6 K $\leq$ $T$ 300 K. Our reveals cooperative distortions of $T$O$_6$ octahedral for all Jahn-Teller active ions = Mn$^{3+}$, Ti$^{3+}$ Co$^{3+}$, which confirmed by X-ray photoelectron spectroscopy. Two specific compositions ($x$ 0.2 0.4) have been chosen because their unique features: noncollinear...
We present magnetization measurements carried out on polycrystalline and single-crystalline samples of $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ under hydrostatic pressures up to 2 GPa establish the temperature-pressure phase diagram this material. The N\'eel temperature (${T}_{\mathrm{N}}$) is slightly enhanced upon compression with $d{T}_{\mathrm{N}}/dp$ = 1.5 K/GPa. Above 1.2 GPa, undergoes a first-order transition toward nonmagnetic dimerized phase, no...
We report on isothermal magnetization, M\"ossbauer spectroscopy, and magnetostriction as well temperature-dependent alternating-current (ac) susceptibility, specific heat, thermal expansion of single crystalline polycrystalline ${\mathrm{Li}}_{2}({\mathrm{Li}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x})\text{N}$ with $x=0$ $x\ensuremath{\approx}0.30$. Magnetic hysteresis emerges at temperatures below $T\ensuremath{\approx}50\phantom{\rule{4pt}{0ex}}\mathrm{K}$ coercivity fields up to...
A well-known feature of CaFe$_{2}$As$_{2}$-based superconductors is the pressure-induced collapsed tetragonal phase that commonly ascribed to formation an interlayer As-As bond. Using detailed X-ray scattering and spectroscopy, we find Rh-doped Ca$_{0.8}$Sr$_{0.2}$Fe$_{2}$As$_{2}$ does not undergo a first-order transition local Fe moments persist despite bonds. Our density functional theory calculations reveal Fe-As bond geometry critical for stabilizing magnetism drop in $c$ lattice...
The organic charge-transfer salt EtMe${}_{3}$P[Pd(dmit)${}_{2}$]${}_{2}$ is a quasi-two-dimensional Mott insulator with localized spins $S=1/2$ residing on distorted triangular lattice. Here we report measurements of the uniaxial thermal expansion coefficients ${\ensuremath{\alpha}}_{i}$ along in-plane $i=a$ and $c$ axis as well out-of-plane $b$ for temperatures 1.4 $\text{K}\ensuremath{\le}T\ensuremath{\le}200$ K. Particular attention paid to lattice effects around phase transition at...
Single crystals of Ca(Fe1-xRux)2As2 (0<x<0.065) and Ca1-yLay(Fe0.973Ru0.027)2As2 (0<y<0.2) have been synthesized studied with respect to their structural, electronic magnetic properties. The partial substitution Fe by Ru induces a decrease the c-axis constant leading for x<0.023 suppression coupled structural (tetragonal orthorhombic) transitions. At x_cr=0.023 first order transition collapsed tetragonal (CT) phase is found, which behaves like Fermi liquid stabilized further increase x....
A detailed investigation of the charge-ordered charge-transfer salt \delta-(EDT-TTF-CONMe$_{2}$)$_{2}$Br by thermal-expansion measurements and dielectric spectroscopy reveals three dynamic processes relaxational character. The slowest one exhibits characteristics glassy freezing is ascribed to conformational dynamics terminal ethylene groups organic molecules. Such a process was previously found for related salts where, however, anions form polymerlike chains, in contrast spherical present...
In double perovskite oxides (${A}_{2}{BB}^{\ensuremath{'}}{\mathrm{O}}_{6}$), magnetism often arises from diluted magnetic lattices, created by combining a structure with localized $3d$ elements ($B$) alongside another lattice containing nearly nonmagnetic delocalized $4d/5d$ (${B}^{\ensuremath{'}}$). Alternatively, the can consist entirely of elements, one being completely ${d}^{0}$ state. ${\mathrm{La}}_{2}{\mathrm{CoTiO}}_{6}$ (LCTO), representative oxide, contains Ti in state electron...
Abstract Measurements of the coefficient thermal expansion on spin‐liquid candidate κ‐(BEDT‐TTF) 2 Cu (CN) 3 have revealed distinct and strongly anisotropic lattice effects around 6 K – a possible spin liquid instability. In order to study magnetic field low‐temperature state, dilatometric measurements been conducted both as function temperature at B = const. T const . While anomaly is found be insensitive fields ≤ 10 T, maximum applied, surprisingly strong ‐induced are observed for applied...