arXiv subjects

A. Poddar

Publications and source records attributed to A. Poddar.

4 recordsLinked to original sources

arXiv2013

Scaling of NonOhmic Conduction in Strongly Correlated Systems

A new scaling formalism is used to analyze nonlinear I-V data in the vicinity of metal-insulator transitions (MIT) in five manganite systems. An exponent, called the nonlinearity exponent, and an onset field for nonlinearity, both characteristic of the system under study, are obtained from the analysis. The onset field is found to have an anomalously low value corroborating the theoretically predicted electronically soft phases. The scaling functions above and below the MIT of a polycrystalline sample are found to be the same but with different exponents which are attributed to the distribution of the MIT temperatures. The applicability of the scaling in manganites underlines the universal response of the disordered systems to electric field.

cond-mat.dis-nn↗

arXiv2012

Evidence of structural phase transition in superconducting SmFeAsO_(1-x)F_x from 19^F NMR

We report the resistivity, magnetization and 19^F NMR results in polycrystalline sample of SmFeAsO_(0.86)F_(0.14). The resistivity and the magnetization data show a sharp drop at 48 K indicating the superconducting transition. The nuclear spin-lattice rate (1/T_1) and spin-spin relaxation rate (1/T_2) clearly show the existence of a structural phase transition near 163 K in the sample which also undergo superconducting transition. This finding creates interest to explore whether this is unique for only Sm based systems or it is also present in other rare-earth based 1111 superconductors.

cond-mat.supr-con↗

arXiv2008

Magnetic Response of NiFe2O4 nanoparticles in polymer matrix

We report the magnetic properties of magnetic nano-composite, consisting of different quantity of NiFe2O4 nanoparticles in polymer matrix. The nanoparticles exhibited a typical magnetization blocking, which is sensitive on the variation of magnetic field, mode of zero field cooled/field cooled experiments and particle quantity in the matrix. The samples with lower particle quantity showed an upturn of magnetization down to 5 K, whereas the blocking of magnetization dominates at lower temperatures as the particle quantity increases in the polymer. We examine such magnetic behaviour in terms of the competitive magnetic ordering between core and surface spins of nanoparticles, taking into account the effect of inter-particle (dipole-dipole) interactions on nanoparticle magnetic dynamics.

cond-mat.mtrl-sci↗

arXiv1996

Irreversible magnetization in thin YBCO films rotated in external magnetic field

The magnetization M of a thin YBaCuO film is measured as a function of the angle $θ$ between the applied field H and the c-axis. For fields above the first critical field, but below the Bean's field for first penetration H*, M is symmetric with respect to $θ=π$ and the magnetization curves for forward and backward rotation coincide. For H>H* the curves are asymmetric and they do not coincide. These phenomena have a simple explanation in the framework of the Bean critical state model.

supr-con↗