• Devinder Singh

      Articles written in Journal of Chemical Sciences

    • Preparation and study of structural electrical and magnetic properties of La2SrFe2O7 and La2SrMn2O7

      Indu Bhushan Sharma Devinder Singh

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      Ruddlesden-Popper type phases La2SrFe2O7 and La2SrMn2O7 have been prepared by traditional ceramic method and their crystal structure has been determined by powder X-ray diffraction study. The iron compound has a tetragonal unit cell witha=3·916 Å andc=20·463 Å, while the phase containing manganese hasa=3·868 Å andc=20·205 Å in the space groupI4/mmm. La2SrMn2O7 is ferromagnetic in the temperature 77–300 K and exhibits spin state transition above 210K, while La2SrFe2O7 is antiferromagnetic. Both the phases are insulators and electrical conduction in La2SrMn2O7 is a function of transition in magnetic behaviour of the metal ion Mn3+, while insulator behaviour is more pronounced in La2SrFe2O7.

    • Preparation and study of structure, electric transport and magnetic properties of Sr3Ru2O7 and Sr3Ru1.5Fe0.5O7

      Indu B Sharma Devinder Singh

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      Sr3Ru2O7 and Sr3Ru1.5Fe0.5O7 have been prepared by the ceramic method. XRD studies show that the phases crystallize as tetragonal unit cells with the space groupI4/mmm. Electric conduction in these phases follows variable range-hopping mechanism but the characteristic energy of hopping in Sr3Ru2O7 is reduced to a great extent. Magnetic susceptibility of Sr3Ru2O7 shows an abrupt rise below 200 K. Sr3Ru1.5Fe0.5O7 is antiferromagnetic.

    • Synthesis and characterization of Ruddlesden-Popper (RP) type phase LaSr2MnCrO7

      Devinder Singh Rajinder Singh

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      New Ruddlesden-Popper (RP) type phase LaSr2MnCrO7 has been synthesized by ceramic method. Rietveld profile analysis shows that the phase crystallizes with tetragonal unit cell in the space group I4/mmm. The electrical resistivity of the phase has been measured in the temperature range of 10-300 K using Leybold closed cycle helium cryostat. The phase shows insulator-metal (I-M) transition at low temperature, the phenomenon often associated with giant magnetoresistance. 3D variable range hopping governs the electrical conduction in the insulator region above the I-M transition temperature. Magnetic susceptibility of the phase has been measured in the temperature range of 100-300 K. Magnetic studies suggest that the phase is ferromagnetic.

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