Dinesh Varshney

Thermal conductivity analysis of lanthanum doped manganites

The temperature-dependent thermal conductivity of the doped manganites La0.7Ca0.3MnO3 is theoretically analyzed within the framework of Kubo formulae. The Hamiltonian consists of phonon, electron and magnon thermal conductivity contribution term. In this process we took defects, carrier, grain boundary, scattering process term and then calculate phonon, electron and magnon thermal conductivity.

Influence of Co doping on structural and electrical properties of La0.5Ce0.5Mn1−xCoxO3 manganites

The effect of Co doping on structural, electrical and magnetic properties of half doped La0.5Ce0.5Mn1−xCoxO3 (x = 0, 0.05) is investigated. The structure of the compounds crystallizes in to orthorhombically distorted perovskite structure. The electrical resistivity of La0.5Ce0.5MnO3 exhibits metal-semiconductor transition (TMS ∼ 225 K). However, La0.5Ce0.5Mn1−xCo0.05O3 manganites show semiconducting behavior throughout temperature range. The magnetic susceptibility measurement confirms that both the samples undergo a transition from paramagnetic to ferromagnetic phase. The metallic resistivity (T < TMS) is analyzed by considering the electron-electron, electron-phonon and spin fluctuation mechanism while semiconducting resistivity is fitted with small polaron conduction model.

Structure and electrical resistivity behavior of barium doped LaMnO3 manganite

Structural and transport properties of La0.7Ba0.3MnO3 have been experimentally investigated. La0.7Ba0.3MnO3 crystallizes in single phase with hexagonal symmetry (R.3c space group setting) and the metal semiconducting transition at about 220 K (H = 0 T). Low temperature minimum resistivity (0 T) shows signature of electron-electron and Kondo-like spin dependent scattering. However, for fields of about 8 T, minimum resistivity documents a disappearance of Kondo-like spin dependent scattering. Metallic resistivity is successfully explained with spin-fluctuation, phonon and electron-electron scattering mechanism. Semiconducting characteristic is well retraced by small polaron conduction model and the activation energy slightly suppresses on the application of field.

Electrical, Magnetic and Thermal Transport Behavior of Divalent/Tetravalent Doped LaMnO3 Manganites

We report the investigations of electrical magnetic and thermal properties of La0.7−x CexCa0.3MnO3 (0.00.3) manganites. The metal‐semiconducting transitions (TMS) are observed for all doped manganites at ∼255 K, ∼235 K ∼220 K and ∼154 K. The magnetic susceptibility measurement confirms that the sample undergoes a transition from paramagnetic to ferromagnetic phase at a particular temperature (TC). It is noticed that the TC is nearly equal to the TMS. Specific heat measurements depict a pronounced anomaly near the TC, indicating the magnetic ordering and magnetic inhomogeneity in the samples.