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10 results on '"Mandal, Golak"'

1. Revised crystal structure and electronic properties of high dielectric Ba(Fe$_{1/2}$Nb$_{1/2}$)O$_{3}$ ceramics

Author

Ray, Rajyavardhan, Himanshu, A. K., Mandal, Golak K., Kumar, Uday, Jha, S. N., Patra, N, Bhattacharya, D., Shinde, A. B., Richter, Manuel, and Krishna, P. S. R.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

Ba(Fe$_{1/2}$Nb$_{1/2}$)O$_3$ (BFN) ceramics are considered to be promising for technological applications owing to their high dielectric constant over a wide range of temperatures. However, there exists considerable discrepancy over the structural details. We address this discrepancy through a combined x-ray diffraction at room temperature and neutron powder diffraction measurements in the range from 5K up to room temperature, supplemented by a comparative analysis of the earlier reported structures. Our study reveals a cubic structure with space group Pm$\bar{3}$m at all measured temperatures. Further, the x-ray near edge structure and the extended x-ray absorption fine structure studies on the local environment of the Fe ions is consistent with the cubic symmetry. An appropriate value of $U$ for DFT+$U$ calculations is obtained by comparison with x-ray absorption spectroscopy, which agrees well with the earlier reported electronic properties., Comment: 15 pages, 9 figures

Published
2019
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2. Revised crystal structure and electronic properties of high dielectric Ba(Fe1/2Nb1/2)O3 ceramics.

Author

Ray, Rajyavardhan, Himanshu, A. K., Mandal, Golak K., Kumar, Uday, Jha, S. N., Patra, N., Bhattacharya, D., Shinde, A. B., Richter, Manuel, and Krishna, P. S. R.

Subjects
X-ray absorption near edge structure, POWDERS, EXTENDED X-ray absorption fine structure, ELECTRONIC structure, CRYSTAL structure, DIELECTRIC properties, SPACE groups
Abstract

Ba (Fe 1 / 2 Nb 1 / 2) O 3 ceramics are considered to be promising for technological applications owing to their high dielectric constant over a wide range of temperatures. However, there exists considerable discrepancy over the structural details. We address this discrepancy through a combined x-ray diffraction at room temperature and neutron powder diffraction measurements in the range from 5 K up to room temperature, supplemented by a comparative analysis of the earlier reported structures. Our study reveals a cubic structure with space group P m 3 ¯ m at all measured temperatures. Further, the x-ray near edge structure and extended x-ray absorption fine structure studies on the local environment of the Fe ions is consistent with the cubic symmetry. An appropriate value of U for DFT+ U calculations is obtained by comparison with x-ray absorption spectroscopy, which agrees well with the earlier reported electronic properties. [ABSTRACT FROM AUTHOR]

Published
2021
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7. Optical and Electronic Structure studies of half metallic in Sr2CoWO6 double perovskite.

Author

Mandal, Golak, Jha, Dhiraj, Himanshu, A. K., Mukherjee, P., Das, N. K., Singh, B. K., Kumar, Uday, and Sinha, T. P.

Subjects
*STRONTIUM compounds, *ELECTRONIC structure, *PEROVSKITE, *OPTICAL properties of metals, *ELECTRIC properties of metals, *DENSITY functional theory
Abstract

The density function theory (DFT) under the generalised gradient approximation has been used to investigate the electronic structure of the double perovskite half metallic Sr2CoWO6 synthesied by the solid state reaction technique. The band gap of the system was measured from the Uv-Vis spectra and compared with the theoretically calculated values. Our results states that Sr2CoWO6 material behaves as insulators for the spin-up orientation and spindown orientation as found for the half metallic systems. [ABSTRACT FROM AUTHOR]

Published
2017
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8. Ab Initio study of double perovskites Ba2DySbO6.

Author

Jha, Dhiraj Kumar, Mandal, Golak, Ray, Chandan, Himanshu, A. K., Singh, B. K., Kumar, Uday, and Choudhary, B. K.

Subjects
*PEROVSKITE, *BARIUM compounds, *ELECTRONIC band structure, *DENSITY functional theory, *ELECTRON-electron interactions
Abstract

First principle study of the electronic band structure of Ba2DySbO6 synthesied by the solid state reaction technique have been performed within the framework of density function theory using WIEN2K. It has been shown in the absence of electron-electron interaction (U=0), BaDySO6 behaves like a half-metal. Even in the presence of DFT+U, electron-electron interaction via the Hubbard term (from U = 0, 2.72e -7.02eV), it still shows half metals. [ABSTRACT FROM AUTHOR]

Published
2016
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9. Ab Initio study of double perovskites Ba2DySbO6.

Author

Jha, Dhiraj Kumar, Mandal, Golak, Ray, Chandan, Himanshu, A. K., Singh, B. K., Kumar, Uday, and Choudhary, B. K.

Subjects
PEROVSKITE, BARIUM compounds, ELECTRONIC band structure, DENSITY functional theory, ELECTRON-electron interactions
Abstract

First principle study of the electronic band structure of Ba2DySbO6 synthesied by the solid state reaction technique have been performed within the framework of density function theory using WIEN2K. It has been shown in the absence of electron-electron interaction (U=0), BaDySO6 behaves like a half-metal. Even in the presence of DFT+U, electron-electron interaction via the Hubbard term (from U = 0, 2.72e -7.02eV), it still shows half metals. [ABSTRACT FROM AUTHOR]

Published
2016
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10. Electronic structure calculation of Sr2CoWO6 double perovskite using DFT+U.

Author

Mandal, Golak, Jha, Dhiraj, Himanshu, A. K., Ray, Rajyavardhan, Mukherjee, P., Das, Nisith, Singh, B. K., Sreenivas, K., Singh, M. N., Sinha, A. K., Singh, Biswas, and Das

Subjects
*SYNCHROTRONS, *RAMAN spectroscopy, *LATTICE constants, *DENSITY functional theory, *ELECTRIC insulators & insulation, *SEMIMETALS, *BAND gaps
Abstract

Using the synchrotron and Raman spectroscopy we measured the lattice parameter and Raman modes of the half-metallic (HM) Sr2CoWO6 (SCoW) synthesied by the solid state reaction technique.. The physical properties of SCoW are studies within the framework of density function theory (DFT) under the generalised gradient approximation (GGA) of Perdew, Bruke, and Ernzerhof both by itself and including a coulomb repulsion via the Hubbard approach or GGA+U. Our results states that Sr2CoWO6 material behaves as insulators for the spin-up orientation and spindown orientation as found for the half metallic systems and at U = 0.06eV the ground state of spin up channel being insulating with spin gap of 2.27eV comparable to the experimental Band gap (BG). [ABSTRACT FROM AUTHOR]

Published
2018
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