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Birabar Nanda

Bio: Birabar Nanda is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Band gap & Ferromagnetism. The author has an hindex of 17, co-authored 73 publications receiving 1046 citations. Previous affiliations of Birabar Nanda include Indian Institutes of Technology & University of Missouri.


Papers
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TL;DR: In this article, the electronic and magnetic properties of tetragonal LaMnO 3 (LMO) under uniaxial strain, appropriate for epitaxially grown LMO heterostructures, from density functional calculations were studied.

10 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined the effect of inversion symmetry breaking (ISB) field and hydrostatic pressure on the band topology of halide perovskites by taking ${\mathrm{MAPbI}}_{3}$ as a representative.
Abstract: Through model Hamiltonian studies and first-principle electronic structure calculations, we have examined the effect of inversion symmetry breaking (ISB) field and hydrostatic pressure on the band topology of halide perovskites by taking ${\mathrm{MAPbI}}_{3}$ as a representative. Our study shows that while hydrostatic pressure induces normal to topological insulator continuous phase transition, the ISB field makes it first order. The pressure smoothly reduces the normal band gap, and without ISB, the system achieves a gapless state before it produces a nontrivial band gap with inverted characters. The ISB field does not stabilize the gapless state, and therefore, the discontinuity in the band gap with pressure gives rise to the first-order transition. Furthermore, in the nontrivial phase, the ISB field forms an invariant surface Dirac circle in the neighborhood of TRIM, which is the first of its kind. The circle is formed due to interpenetration of Dirac cones resembling the band topology of AA-stacked bilayer graphene.

10 citations

Journal ArticleDOI
24 Oct 2017
TL;DR: In this paper, the magnetic properties of microstrain-controlled Bi1−x Ca x Fe1−y Ti y O3−δ (y = 0 and x = y) nanoparticles are analyzed as a function of their size ranging from 18 nm to 200 nm.
Abstract: Magnetization of antiferromagnetic nanoparticles is known to generally scale up inversely to their diameter (d) according to Neel's model. Here we report a deviation from this conventional linear 1/d dependence, altered significantly by the microstrain, in Ca and Ti substituted BiFeO3 nanoparticles. Magnetic properties of microstrain-controlled Bi1−x Ca x Fe1−y Ti y O3−δ (y = 0 and x = y) nanoparticles are analyzed as a function of their size ranging from 18 nm to 200 nm. A complex interdependence of doping concentration (x or y), annealing temperature (T), microstrain (e) and particle size (d) is established. X-ray diffraction studies reveal a linear variation of microstrain with inverse particle size, 1/d nm−1 (i.e. e d = 16.5 nm%). A rapid increase in the saturation magnetization below a critical size d c ~ 35 nm, exhibiting a (1/d) α (α ≈ 2.6) dependence, is attributed to the influence of microstrain. We propose an empirical formula M (1/d)e β (β ≈ 1.6) to highlight the contributions from both the size and microstrain towards the total magnetization in the doped systems. The magnetization observed in nanoparticles is thus, a result of the competing magnetic contribution from the terminated spin cycloid on the surface and counteracting microstrain present at a given size.

10 citations

Journal ArticleDOI
20 Mar 2019
TL;DR: In this paper, it was shown that 33 % fluorination is sufficient to shift the Fermi level (E$_F$) by 2 eV so that the invariant Dirac state lies on it to make BaBiO$_2$F a topological insulator.
Abstract: The disadvantage of BaBiO$_3$ of not being a topological insulator despite having symmetry protected Dirac state is overcome by shifting the Fermi level (E$_F$) via fluorination. The DFT calculations reveal that the fluorination neither affects the spin-orbit coupling nor the parity of the states, but it acts as a perfect electron donor to shift the E$_F$. We find that 33 % fluorination is sufficient to shift the E$_F$ by $\sim$ 2 eV so that the invariant Dirac state lies on it to make BaBiO$_2$F a topological insulator. The fluorinated cubic compound can be experimentally synthesized as the phonon studies predict dynamical stability above $\sim$ 500 K. Furthermore, the Dirac states are found to be invariant against the low-temperature phase lattice distortion which makes the structure monoclinic. The results carry practical significance as they open up the possibility of converting the family of superconducting oxides, ABiO$_3$ (A = Na, K, Cs, Ba, Sr, Ca), to real topological insulator through appropriate fluorination.

9 citations

Journal ArticleDOI
TL;DR: In this article, the mechanism of NO2 interaction on semiconductor surfaces such as TiO2 is investigated and a key step in designing the catalytic processes for converting NO2 to useful products.
Abstract: Understanding the mechanism of NO2 interaction on semiconductor surfaces such as TiO2 is a key step in designing the catalytic processes for conversion of NO2 to useful products. In the present wor...

9 citations


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TL;DR: The experimental and theoretical state-of-art concerning spin injection and transport, defect-induced magnetic moments, spin-orbit coupling and spin relaxation in graphene are reviewed.
Abstract: The isolation of graphene has triggered an avalanche of studies into the spin-dependent physical properties of this material, as well as graphene-based spintronic devices Here we review the experimental and theoretical state-of-art concerning spin injection and transport, defect-induced magnetic moments, spin-orbit coupling and spin relaxation in graphene Future research in graphene spintronics will need to address the development of applications such as spin transistors and spin logic devices, as well as exotic physical properties including topological states and proximity-induced phenomena in graphene and other 2D materials

1,329 citations

Journal ArticleDOI
TL;DR: The tight-binding model is used to describe optical and transport properties including the integer quantum Hall effect, and the also discusses orbital magnetism, phonons and the influence of strain on electronic properties.
Abstract: We review the electronic properties of bilayer graphene, beginning with a description of the tight-binding model of bilayer graphene and the derivation of the effective Hamiltonian describing massive chiral quasiparticles in two parabolic bands at low energies. We take into account five tight-binding parameters of the Slonczewski–Weiss–McClure model of bulk graphite plus intra- and interlayer asymmetry between atomic sites which induce band gaps in the low-energy spectrum. The Hartree model of screening and band-gap opening due to interlayer asymmetry in the presence of external gates is presented. The tight-binding model is used to describe optical and transport properties including the integer quantum Hall effect, and we also discuss orbital magnetism, phonons and the influence of strain on electronic properties. We conclude with an overview of electronic interaction effects.

797 citations

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TL;DR: This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces, identifying the most exciting new scientific results and pointing to promising future research directions.
Abstract: This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces. It provides a historical background and literature survey, but focuses on recent progress, identifying the most exciting new scientific results and pointing to promising future research directions. It starts with an introduction and overview of how basic magnetic properties are affected by interfaces, then turns to a discussion of charge and spin transport through and near interfaces and how these can be used to control the properties of the magnetic layer. Important concepts include spin accumulation, spin currents, spin transfer torque, and spin pumping. An overview is provided to the current state of knowledge and existing review literature on interfacial effects such as exchange bias, exchange spring magnets, spin Hall effect, oxide heterostructures, and topological insulators. The article highlights recent discoveries of interface-induced magnetism and non-collinear spin textures, non-linear dynamics including spin torque transfer and magnetization reversal induced by interfaces, and interfacial effects in ultrafast magnetization processes.

758 citations

Journal ArticleDOI
TL;DR: A review of new developments in theoretical and experimental electronic-structure investigations of half-metallic ferromagnets (HMFs) is presented in this article, where the effects of electron-magnon interaction in HMFs and their manifestations in magnetic, spectral, thermodynamic, and transport properties are considered.
Abstract: A review of new developments in theoretical and experimental electronic-structure investigations of half-metallic ferromagnets (HMFs) is presented. Being semiconductors for one spin projection and metals for another, these substances are promising magnetic materials for applications in spintronics (i.e., spin-dependent electronics). Classification of HMFs by the peculiarities of their electronic structure and chemical bonding is discussed. The effects of electron-magnon interaction in HMFs and their manifestations in magnetic, spectral, thermodynamic, and transport properties are considered. Special attention is paid to the appearance of nonquasiparticle states in the energy gap, which provide an instructive example of essentially many-body features in the electronic structure. State-of-the-art electronic calculations for correlated d-systems are discussed, and results for specific HMFs (Heusler alloys, zinc-blende structure compounds, CrO2, and Fe3O4) are reviewed.

748 citations