A5078911883- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Nuclear materials and radiation effects
- Multiferroics and related materials
- Rare-earth and actinide compounds
- Iron-based superconductors research
- X-ray Diffraction in Crystallography
- Advanced Thermoelectric Materials and Devices
- Magnetic Properties of Alloys
- Crystallization and Solubility Studies
- Heusler alloys: electronic and magnetic properties
- Theoretical and Computational Physics
- Topological Materials and Phenomena
- High-pressure geophysics and materials
- Crystallography and molecular interactions
- Magnetic properties of thin films
- Ferroelectric and Piezoelectric Materials
- Quantum and electron transport phenomena
- MXene and MAX Phase Materials
- Magnetic Properties and Synthesis of Ferrites
- Chalcogenide Semiconductor Thin Films
- Geological and Geochemical Analysis
- 2D Materials and Applications
- Quantum, superfluid, helium dynamics
Indian Institute of Science Education and Research Pune
2016-2025
Wright State University
2017
Université Paris-Sud
2007-2013
Leibniz Association
2013
Centre National de la Recherche Scientifique
2008-2012
Institut de Chimie Moléculaire et des Matériaux d'Orsay
2011-2012
Indian Institute of Science Bangalore
2012
Leibniz Institute for Solid State and Materials Research
2010-2012
Université Paris-Saclay
2012
Tata Institute of Fundamental Research
2001-2010
One-dimensional (1D) magnetic insulators have attracted significant interest as a platform for studying emergent phenomena such quasiparticle fractionalization and quantum criticality. The antiferromagnetic Heisenberg chain of spins-1/2 is an important reference system; its elementary excitations are spin-1/2 quasiparticles called spinons that always created in pairs. However, while inelastic neutron scattering (INS) experiments routinely observe the excitation continuum associated with...
We present here magnetization, specific heat, and Raman studies on single-crystalline specimens of the first pyrochlore member ${\mathrm{Sm}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ rare-earth titanate series. Its analogous compound ${\mathrm{Sm}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ in zirconate series is also investigated polycrystalline form. The Sm spins remain unordered down to at least $T=0.5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. absence magnetic ordering attributed very small values...
We present here temperature-dependent Raman, x-ray diffraction, and specific heat studies between room temperature 12 K on single crystals of spin-ice pyrochlore compound ${\text{Dy}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$ its nonmagnetic analog ${\text{Lu}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$. Raman data show a ``new'' band not predicted by factor group analysis Raman-active modes for the structure in ${\text{Dy}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$, appearing below ${T}_{c}=110\text{ }\text{K}$...
In transition metal oxides, quantum confinement arising from a large surface to volume ratio often gives rise novel physico-chemical properties at nanoscale. Their size dependent have potential applications in diverse areas, including therapeutics, imaging, electronic devices, communication systems, sensors, and catalysis. We analyzed structural, magnetic, dielectric, thermal of weakly ferromagnetic SmFeO3 nanoparticles sizes about 55 nm 500 nm. The nano-size particles exhibit several...
Ho-doped sample simultaneously exhibits high-coercivity and enhanced remnant magnetization with a polar <italic>R</italic>3<italic>c</italic> symmetry at room temperature. The onset of to <italic>Pnma</italic> phase transition is observed high temperatures in the samples.
Ag2Se is a potentially useful material with interesting magnetoresistive and thermoelectric properties. In several recent studies, the figure of merit (zT) has been shown to approach 1 near 380 K (i.e., about 25 below its superionic transition temperature). However, what plagues use in real life applications sample dependence very poor reproducibility. work, it clearly established that root cause this Ag migration during high-temperature sintering or melting. Here, we show high-density...
High-entropy alloys (HEAs) have gained significant attention recently due to their exceptional physical properties. Among HEAs, entropy-stabilized alloys, where the high configurational entropy drives structural stability, are of considerable interest in new materials discovery. Here, we combine theoretical and experimental approaches design very low lattice thermal conductivity (κl) high-entropy (TiHf)1/2(Fe1–xCoNi1+x)1/3Sb belonging half-Heusler family. We demonstrate that...
We have developed a versatile, fully automated Hall measurement setup for operations between room temperature and 750 K in magnetic fields up to ±10 kOe. Our compact sample holder design with localized heating minimal heat losses enables precise stability (better than mK at K) low power consumption (20–25 W). The is housed within 26 mm air gap the pole pieces of an electromagnet. holder, enclosed quartz tube controlled atmosphere, can accommodate various shapes sizes, which be contacted...
The S=1/2 spin chain material SrCuO2 doped with 1% S=1 Ni-impurities is studied by inelastic neutron scattering. At low temperatures, the spectrum shows a pseudogap \Delta ~ 8 meV, absent in parent compound, and not related to any structural phase transition. shown be generic feature of quantum chains dilute defects. A simple model based on this idea quantitatively accounts for exprimental data measured temperature range 2-300 K, allows represent momentum-integrated dynamic structure factor...
We have carried out temperature- and pressure-dependent Raman x-ray measurements on single crystals of ${\text{Tb}}_{2}{\text{Ti}}_{2}{\text{O}}_{7}$. attribute the observed anomalous temperature dependence phonons to phonon-phonon anharmonic interactions. The quasiharmonic contributions temperature-dependent changes in phonon frequencies are estimated quantitatively using mode Gr\"uneisen parameters derived from experiments bulk modulus high-pressure measurements. Further, our data suggest...
Thirty-five years ago, Sanders and Walton [Phys. Rev. B 15, 1489 (1977)] proposed a method to measure the phonon-magnon interaction in antiferromagnets through thermal transport which so far has not been verified experimentally. We show that dynamical variant of this approach allows direct extraction equilibration time, yielding 400 μs for cuprate spin-ladder system Ca(9)La(5)Cu(24)O(41). The present work provides general directly address spin-phonon by means experiments.
We have investigated the thermal conductivity κmag of high-purity single crystals spin chain compound Sr2CuO3, which is considered an excellent realization one-dimensional spin-1/2 antiferromagnetic Heisenberg model. find that spinon heat strongly enhanced as compared to previous results obtained on samples with lower chemical purity. The analysis allows computation mean free path lmag a function temperature. At low temperature we ∼ 0.5 µm, corresponding more than 1200 unit cells. Upon...
The pyrochlore ${\mathrm{Eu}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ has recently attracted significant attention as a candidate Weyl semimetal. previous reports on this compound unanimously show thermally induced metal-to-insulator (MI) transition, concomitant with antiferromagnetic long-range ordering of the Ir moments below ${T}_{\mathit{N}}\ensuremath{\sim}120$ K. However, there are contradictory concerning slope $d\ensuremath{\rho}/dT$ resistivity plots ($\ensuremath{\rho}$) in...
MoTe2 has a stable hexagonal semiconducting phase (2H) as well two semimetallic phases with monoclinic (1T′) and orthorhombic (Td) structures. A structural change can thus be accompanied by significant in electronic transport properties. The are connected temperature driven transition could exhibit topological Here we make extensive Raman measurements function of layer thickness, temperature, electrostatic doping on few 2H-MoTe2 also 1T′-MoTe2 Td-WTe2. Recent work raised the possibility...
We report high-resolution dilatometry on high-quality single crystals of ${\mathrm{NiTiO}}_{3}$ grown by means the optical floating-zone technique. The anisotropic magnetic phase diagram is constructed from thermal expansion and magnetostriction studies up to $B=15\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ magnetization in static (15-T) pulsed (60-T) fields. Our data allow us quantitatively study magnetoelastic coupling determine uniaxial pressure dependencies. While entropy changes are found...
High-quality single crystals of ${\mathrm{CoTiO}}_{3}$ are grown and used to elucidate in detail structural magnetostructural effects by means high-resolution capacitance dilatometry studies fields up 15 T which complemented specific heat magnetization measurements. In addition, we refine the single-crystal structure ilmenite ($R\overline{3}$) phase. At antiferromagnetic ordering temperature ${T}_{\mathrm{N}}$ pronounced $\ensuremath{\lambda}$-shaped anomaly thermal expansion coefficients...
Synchrotron-based X-ray diffraction was used to study the phase diagrams and determine compressibilities of pyrochlore rare-earth titanates Ho2Ti2O7, Y2Ti2O7 Tb2Ti2O7 ∼50 GPa. The bulk moduli cubic these materials were calculated be 213±2, 204±3 199±1 GPa, respectively. onset a structural change from monoclinic observed near 37, 42 39 modulus for high pressure has been determined 185±3
We study the pyrochlore series (Eu$_{1-x}$Bi$_x$)$_2$Ir$_2$O$_7$ for $ 0 \leq x 1$. show that small $x$, lattice undergoes an anomalous contraction but all-in/all-out and metal-to-insulator transitions remain robust, resistivity approaches a $1/T$ dependence at low-T, suggesting proximity to Weyl semimetallic phase, as previously predicted theoretically. At boundary between Eu$_2$Ir$_2$O$_7$ Bi$_2$Ir$_2$O$_7$ qualitatively different ground state emerges, which is characterized by its unusual...
Observation of an enhanced Curie tail in the low temperature susceptibility indicates presence uncompensated spins at ends CuSe<sub>2</sub>O<sub>5</sub>nanorods. The curie also contributes towards shift hump CuSe<sub>2</sub>O<sub>5</sub>nanorods to ∼75 K (from ∼101 for single crystal).
We report temperature-dependent Raman scattering and X-ray diffraction studies of pyrochlore iridates, (Eu$_{1-x}$Bi$_x$)$_2$Ir$_2$O$_7$, for x=0, 0.02, 0.035, 0.05 0.1. The temperature variation in experiments spans from 4 K to 300 K, covering the metal-insulator phase transition accompanied by paramagnetic all-in/all-out (AIAO) spin ordering (T$_N$). These systems also show a Weyl semi-metal (WSM) at low temperatures (below ~50 K). that Ir-O-Ir bond bending mode, A$_{1g}$ (510 cm$^{-1}$),...
Abstract NiPS 3 is a van der Waals antiferromagnet which has been shown to exhibit spin-phonon and spin-charge coupling in the antiferromagnetically ordered state below T N = 155 K. It also rare Ni-based negative charge-transfer-type insulator with Ni valence linear superposition <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>ψ</mml:mi> <mml:mo>=</mml:mo> <mml:mtext> </mml:mtext> </mml:mrow> <mml:mi>α</mml:mi> <mml:msup> <mml:mi>d</mml:mi>...