Asok Poddar

Bio: Asok Poddar is an academic researcher from Saha Institute of Nuclear Physics. The author has contributed to research in topics: Magnetization & Electrical resistivity and conductivity. The author has an hindex of 21, co-authored 100 publications receiving 1394 citations. Previous affiliations of Asok Poddar include Lady Brabourne College & Indian National Association.

Variation of Tc and transport properties with carrier concentration in Y- and Pb-doped Bi-based superconductors.

Abstract: Electrical resistivity, magnetic susceptibility, and the Hall voltage of Bi{sub 2}Sr{sub 2}Ca{sub 1{minus}{ital x}}Y{sub {ital x}}Cu{sub 2}O{sub 8+{ital y}} (Bi 2:2:1:2) and (Bi{sub 1{minus}{ital x}}Pb{sub {ital x}}){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+{ital y}} (Bi 2:2:2:3) samples are measured as a function of temperature. A metal-insulator transition originating from the change of carrier concentration is found in the Bi 2:2:1:2 system at {ital x}{congruent}0.55. Analysis of the electrical resistivity in the insulating region suggests that the transport is governed by a variable-range-hopping mechanism in the low-temperature region and phonon-assisted hopping of polarons in the high-temperature region. A universal dome-shaped {ital T}{sub {ital c}} versus {ital n}{sub {ital H}} variation is observed in the Bi 2:2:1:2 and Bi 2:2:2:3 systems, which is similar to that reported in La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4} and YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} systems. Various normal-state parameters, such as the effective mass of the carrier, Fermi energy, density of states at the Fermi level, and correlation energy, are calculated and compared to those reported in the literature.

Exchange bias in LaFeO3 nanoparticles

Abstract: Nanoparticles of antiferromagnetic LaFeO3 were prepared by the sol–gel method. An exchange bias effect has been observed and is attributed to the exchange coupling between the ferromagnetic shell and antiferromagnetic core of the particles. The results provide clear evidence of the presence of spontaneous exchange bias in this system. After field cooling from room temperature, the exchange bias increases while the coercivity decreases with decreasing temperature. Taking into account the role of thermal activation, the temperature dependence of exchange bias and coercivity has been interpreted in terms of the spontaneous exchange bias mechanism proposed recently. (Some figures in this article are in colour only in the electronic version)

Thermoelectric power of the Bi2Sr2Ca1-xYxCu2O8+y (x=0-1.0) system.

Abstract: The temperature dependence of the thermoelectric power (TEP) of ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Y}}_{\mathit{x}}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathit{y}}$ samples are reported for x=0\char21{}09 in the temperature range 77\char21{}300 K TEP is positive and large for large x and decreases with decreasing x (increasing carrier concentration) TEP is negative for the x=0 sample The results are discussed following strong correlation and the Nagaosa and Lee model

Electrical transport properties and magnetic cluster glass behavior of Nd0.7Sr0.3MnO3 nanoparticles

Abstract: The transport and magnetic properties have been investigated in Nd07Sr03MnO3 nanoparticles prepared by the sol-gel method The resistivity (ρ) increases with the decrease of the particle size due to the enhancement of the grain boundary effect ρ(T) shows two distinct transitions for all the samples such as metal-insulator transition and transition due to the barrier caused by the grain boundary effect The thermopower (S) is found to be negative and at high temperature S follows the adiabatic small polaron hopping theory In the metallic region the spin wave contribution is found to be dominant in the temperature dependence of the thermopower The magnetoresistance (MR) of the ultrafine particles increases with the decrease of particle size indicating substantial contribution from the grain boundaries Spin polarized intergrain tunneling effect plays an important role in the MR of a smaller size particle, whereas in the case of samples of higher dimension spin fluctuation contributes predominantly The

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications.

Abstract: Among the recent developments in metal-organic frameworks (MOFs), porous layered coordination polymers (CPs) have garnered attention due to their modular nature and tunable structures. These factors enable a number of properties and applications, including gas and guest sorption, storage and separation of gases and small molecules, catalysis, luminescence, sensing, magnetism, and energy storage and conversion. Among MOFs, two-dimensional (2D) compounds are also known as 2D CPs or 2D MOFs. Since the discovery of graphene in 2004, 2D materials have also been widely studied. Several 2D MOFs are suitable for exfoliation as ultrathin nanosheets similar to graphene and other 2D materials, making these layered structures useful and unique for various technological applications. Furthermore, these layered structures have fascinating topological networks and entanglements. This review provides an overview of different aspects of 2D MOF layered architectures such as topology, interpenetration, structural transformations, properties, and applications.