S.V. Subramanyam

Ferromagnetic La0.6Pb0.4MnO3 thin films with giant magnetoresistance at 300 K

Highly textured, as-deposited

Colossal magnetoresistance in epitaxial La(1−x−y)NayMnO3 thin film

La_{0.6}Pb_{0.4}MnO_3

Thermal and electrical properties of the novel organic nonlinear crystal L-arginine phosphate monohydrate

thin films have been grown on

Hopping conduction in boron doped amorphous carbon films

LaAlO_3

ENHANCED MAGNETORESISTANCE IN AS-DEPOSITED OXYGEN-DEFICIENT LA0.6PB0.4MNO3-Y THIN FILMS

by pulsed laser deposition. The films are ferromagnetic metals below 300 K. Giant negative magnetoresistance of over 40% is observed at 300 K at 6 T.

ALaMnBO6 (A = Ca, Sr, Ba; B = Fe, Ru) double perovskites

We have synthesized La0.83Na0.11MnO2.93 by heating La2O3 and MnCO3 in NaCl melt at 900 °C. The exact composition was arrived by analyzing each ion by an independent chemical method. The compound crystallized in a rhombohedral structure and showed an insulator-to-metal transition at 290 K. Epitaxial thin films were fabricated on LaAlO3 (100) using a pulsed laser deposition technique. The film also showed an insulator-to-metal transition at 290 K. Magnetoresistance [ΔR/R0=(RH−R0)/R0] was −71% near the insulator-to-metal transition temperature of 290 K at 6 T magnetic field.

Metallic conductivity of amorphous carbon films under high pressure

The thermal expansion, specific heat, dielectric constant, and resistivity of the novel organic nonlinear crystal, L-arginine phosphate monohydrate have been measured as a function of temperature. The thermal expansion is highly anisotropic and has been interpreted on the basis of crystal structure. The dielectric constant and resistivity exhibit a temperature dependence that is similar to that of an ionic crystal. No anomalies are observed in these physical properties from the liquid nitrogen temperature up to its melting point.

Structure and electrical properties of sodium tungsten bronzes thin films

The electrical transport properties of boron doped graphitelike amorphous carbon films have been studied. Variable range hopping (VRH) conduction is found to be the conduction mechanism in these carbon films. The conduction in high temperature regime follows the Mott VRH [J. Non-Cryst. Solids 1, 1 (1968)], whereas a crossover from the Mott [Electronic Process in Non-crystalline Materials (Clarendon, Oxford, 1971)] to the Efros-Shklovskii [J. Phys. C 8, L49 (1975)] VRH is observed at low temperatures. Additional support to this transition is evident from negative magnetoresistance in VRH regime when the sample is deep inside the insulating side of the metal insulator transition. Various calculated parameters such as localization length, density of states at the Fermi level, and Coulomb gap for insulating samples have been estimated from the experimental data. The density of states at the Fermi level shows a gradual shift with a corresponding variation in boron doping level, indicating a change in the density of conducting \pi electrons due to substitutional doping of boron in the carbon network.

Electrical resistivity and enhanced magnetoresistance in (La0.6Pb0.4MnO3/La0.85MnO3−δ)n superlattices

The La0.6Pb0.4MnO3(LPMO) thin films were in situ deposited at different oxygen partial pressure and at a substrate temperature of 630 degrees C by pulsed laser deposition. The films grown at lower oxygen partial pressures showed an increase in lattice parameter and resistivity and a decrease in the insulator-metal transition temperature as compared to the stoichiometric LPMO thin film grown at 400 mTorr. Further, these oxygen-deficient thin films showed over 70% giant magnetoresistance (GMR) near the insulator-metal transition temperature against the 40% GMR in the case of stoichiometric thin films

Study of electrical conduction in polypyrrole by varying the doping level

Abstract We report the synthesis and investigation of electrical and magnetic properties of double perovskites of the formula ALaMnBO 6 for A = Ca, Sr, Ba and B = Fe, Ru. Powder X-ray diffraction (XRD) shows formation of cubic/pseudocubic perovskite structure for all the phases, with no obvious long-range ordering of B-site cations. Electron diffraction, however, reveals an ordering of Mn and Ru in ALaMnRuO 6 , showing a doubling of the primitive cubic perovskite cell. While the B = Fe phases are paramagnetic insulators, the B = Ru phases are ferrimagnetic semiconductors. It is likely that in the B = Ru phases, a valence equilibrium exists between Mn III /Ru IV and Mn II /Ru V states that is biased toward the latter.