A5089206939- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- Electronic and Structural Properties of Oxides
- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Perovskite Materials and Applications
- Multiferroics and related materials
- Electron and X-Ray Spectroscopy Techniques
- Copper-based nanomaterials and applications
- ZnO doping and properties
- Advanced Chemical Physics Studies
- X-ray Diffraction in Crystallography
- Solid-state spectroscopy and crystallography
- Crystallization and Solubility Studies
- Transition Metal Oxide Nanomaterials
- Magnetic properties of thin films
- Semiconductor materials and devices
- Iron-based superconductors research
- 2D Materials and Applications
- Surface and Thin Film Phenomena
- X-ray Spectroscopy and Fluorescence Analysis
- Ferroelectric and Piezoelectric Materials
- Catalysis and Oxidation Reactions
Indian Institute of Science Bangalore
2016-2025
National Institute for Interdisciplinary Science and Technology
2022-2024
Nagpur Institute of Technology
2023
Tezpur University
2023
Uppsala University
2011-2021
Bangalore University
2019
RIKEN Center for Emergent Matter Science
2019
Indian Institute of Science Education and Research Mohali
2019
Jawaharlal Nehru Centre for Advanced Scientific Research
2002-2018
Indian Association for the Cultivation of Science
2007-2017
We have analysed the unusual electronic structure of Sr_2FeMoO_6 combining ab-initio and model Hamiltonian approaches. Our results indicate that there are strong enhancements intraatomic exchange strength at Mo site as well antiferromagnetic coupling between Fe sites. discuss possibility a negative effective Coulomb correlation (U_{eff}) due to these renormalised interaction strengths.
We report magnetic, dielectric, and magnetodielectric responses of the pure monoclinic bulk phase partially disordered ${\mathrm{La}}_{2}{\mathrm{NiMnO}}_{6}$, exhibiting a spectrum unusual properties establish that this compound is an intrinsically multiglass system with large coupling (8%--20%) over wide range temperatures (150--300 K). Specifically, our results unique way to obtain colossal magnetodielectricity, independent any striction effects, by engineering asymmetric hopping...
Abstract The development of high efficiency perovskite solar cells has sparked a multitude measurements on the optical properties these materials. For most studied methylammonium(MA)PbI 3 perovskite, large range (6–55 meV) exciton binding energies been reported by various experiments. existence excitons at room temperature is unclear. MAPb X perovskites we report relativistic Bethe-Salpeter Equation calculations ( GW -BSE). This method capable to directly calculate excitonic from...
Insertion of just a few impurity atoms in host semiconductor nanocrystal can drastically alter its phase, shape, and physical properties. Such doped nanomaterials now constitute an important class optical materials that provide efficient, stable, tunable dopant emission visible NIR spectral windows. Selecting proper dopants inserting them appropriate hosts generate many new series such nanocrystals with several unique attractive properties order to meet current challenges the versatile field...
Charge-storage mechanism of free-standing MoS2/r-GO (r-GO = reduced graphene oxide) hybrid nanoflakes on molybdenum (Mo) foil in Na2SO4 solution is elucidated for realizing a high-performance asymmetric supercapacitor (ASC). Thiourea that acts primarily as sulfur source also helps intercalating ammonium ions, which along with r-GO facilitate situ exfoliation MoS2, producing hierarchical MoS2 expanded interlayer spacing. This expansion facilitates Na+-ions intercalation/deintercalation and...
We report the synthesis of three sizes thioglycerol-capped precipitated ZnS nanocrystallites with relatively narrow size distributions, having average 1.8, 2.5, and 3.5 nm, respectively. These crystallites were extracted as free-standing powders which remain stable under normal atmospheric conditions can be redispersed in suitable solvents. The nanocrystallite characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), (ED), energy dispersive...
he structural, transport, magnetic and optical properties of the double perovskite $A_2$CrWO$_6$ with $A=\text{Sr, Ba, Ca}$ have been studied. By varying alkaline earth ion on $A$ site, influence steric effects Curie temperature $T_C$ saturation magnetization has determined. A maximum $T_C=458$ K was found for Sr$_2$CrWO$_6$ having an almost undistorted structure a tolerance factor $f\simeq 1$. For Ca$_2$CrWO$_6$ Ba$_2$CrWO$_6$ structural changes result in strong reduction $T_C$. Our study...
The electronic structures of a wide range early transition-metal (TM) compounds, including Ti and V oxides with metal valences ranging from 2+ to 5+ formal d-electron numbers 0 2, have been investigated by configuration-interaction cluster model analysis the core-level 2p x-ray photoemission spectra (XPS). Inelastic energy-loss backgrounds calculated experimentally measured electron-energy-loss (EELS) were subtracted XPS remove extrinsic loss features. Parameter values deduced for...
In order to provide a quantitatively accurate description of the band gap variation with sizes in various II-VI semiconductor nanocrystals, we make use recently reported tight-binding parametrization corresponding bulk systems. Using same scheme and parameters, calculate electronic structure nanocrystals real space ranging between 5 80 {\AA} diameter. A comparison available experimental results from literature shows an excellent agreement over entire range sizes.
In the present work, we report synthesis of high quality ZnO nanocrystals with sharp absorption edges in four different sizes, namely 3.0, 3.5, 4.7 and 5.4 nm, characterized by X-ray electron diffraction, as well transmission microscopy. The bandgaps these samples, conjunction further data from published literature, exhibit a systematic dependence on nanocrystal size. absence any prior reliable theoretical results literature to understand this quantitatively, have analyzed for first time,...
We report the synthesis and characterization of several sizes Mn-doped ZnO nanocrystals, both in free-standing capped particle forms. The these nanocrystals could be controlled by capping them with polyvinylpyrollidone under different conditions were estimated X-ray diffraction transmission electron microscopy. absorption properties PVP-capped exhibit an interesting variation band gap concentration Mn. Fluorescence emission, paramagnetic resonance, spectroscopy provide evidence for presence...
A study of the semiconductor-metal transition in series ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CoO}}_{3}$, x=0.0--0.4, using electron-spectroscopy techniques is presented. The results show that ground state ${\mathrm{LaCoO}}_{3}$ has strongly mixed character. From experiments we estimate on-site Coulomb correlation energies ${\mathit{U}}_{\mathit{d}\mathit{d}}$ and ${\mathit{U}}_{\mathit{p}\mathit{p}}$ to be 3.4 6.7 eV, respectively, while...
It is shown that the local spin-density approximation describes well electronic structures of perovskite $\mathrm{La}M{\mathrm{O}}_{3}$ ( $M\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}$ Mn, Fe, Co, Ni) for ground-state and single-electron excited-state properties. Inclusion details crystal distorted from cubic structure crucial to reproduce different magnetic insulating states. Calculated x-ray photoemission spectra are in very good agreement with experimental ones, its angular...
It has been an outstanding problem that a semiconducting host in the bulk form can be doped to large extent, while same nanocrystal is found resist any appreciable level of doping rather stubbornly, this being more acute wurtzite compared zinc blende one. In contrast, our results based on lattice parameter tuning ZnxCd1−xS alloy system achieves ∼7.5% Mn2+ nanocrystal, such concentration substantially higher earlier reports even for hosts with "favorable" zinc-blende structure. These prove...
We have performed steady-state and time-resolved fluorescence studies on undoped Mn-doped ZnS nanocrystals with approximately 16 A diameter. While there is no band-edge emission, the intensity of blue from surface states decreases upon Mn incorporation, which gives rise to an orange emission. These results show that incorporation competes very effectively donor-acceptor for energy transfer electron-hole pair excited across band gap. In both doped samples, establish presence a distribution...
Following growth doping strategy and using dopant oxides nanocrystals as sources, we report here two different transition-metal ions doped in a variety of group II−VI semiconductor nanocrystals. Using manganese oxide copper corresponding intense photoluminescence emission over wide range wavelength has been observed for host Interestingly, this single is successful providing such highly emissive considered here, contrast with the literature reports that would suggest synthesis strategies to...
Electronic structures of electron-doped ${\mathrm{SrTiO}}_{3\ensuremath{-}\ensuremath{\delta}}$ and ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{La}}_{x}{\mathrm{TiO}}_{3}$ have been investigated within the ab initio band-structure approach using a supercell containing eight basic units. A small amount electron doping is found to drive ${\mathrm{SrTiO}}_{3}$ metallic, with Fermi level moving into conduction band in both systems. Clustering oxygen vacancies case gives rise distinct...
Following growth doping technique, highly luminescent (quantum yield > 50%) Mn-doped ZnS nanocrystals are synthesized via colloidal synthetic technique. The dopant emission has been optimized with varying reaction parameters and found the ratio of Zn to S as well percentage introduced in mixture key factors for controlling intensity. method is simple, hassle free, can be scalable gram level without hindering quality nanocrystals. These retain their during various ligand exchange processes...
We study the electronic structure of ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{MnO}}_{3+\mathrm{\ensuremath{\delta}}}$, x=0, 0.1, 0.2, 0.3, and 0.4, across semiconductor-metal transition, using various electron spectroscopy techniques. The negligible intensity seen at ${\mathit{E}}_{\mathit{F}}$ ultraviolet photoemission bremsstrahlung isochromat (BIS) indicate an unusual transition observed for x\ensuremath{\ge}0.2, consistent with resistivity...
Using first-principles density functional calculations, we study the electronic and magnetic properties of ferromagnetic insulating double perovskite compound ${\mathrm{La}}_{2}{\mathrm{NiMnO}}_{6}$, which has been reported to exhibit an interesting field sensitive dielectric anomaly as a function temperature. Our reveals existence very soft infrared active phonons that couple strongly with spins at Ni Mn sites through modification superexchange interaction. We suggest these modes are origin...
Using extensive state-of-the-art experiments over a wide range of synthesis parameters, such as the temperature and concentrations different reactants, we establish qualitatively growth kinetics for ZnO nanocrystals compared to all semiconductor nanocrystals, including ZnO, discussed so far in literature. The rate is shown be strongly dependent on concentration (OH)- an intriguing nonmonotonic manner well almost invariably much slower than well-known generally accepted mechanisms based...