• K Sethupathi

      Articles written in Pramana – Journal of Physics

    • Electrical transport in La1−xCaxMnO3 thin films at low temperatures

      S Angappane K Sethupathi G Rangarajan

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      We report here the low-temperature resistivity of the chemical solution deposited La1−xCaxMnO3 (x=0.2, 0.3 and 0.33) thin films on LaAlO3 substrates. The films were post-annealed in atmosphere at 850°C. The low temperature resistivity data has been studied in order to understand the nature of low-temperature conduction processes. The data showed T2 dependence from 60 K to 120 K consistent with the single magnon scattering process. The deviation from this quadratic temperature dependence at low temperatures is attributed to the collapse of the minority spin band. The two-magnon and electron-phonon processes contribute to scattering of carriers in the temperature range above 120 K.

    • Electrical transport and magnetic ordering in R2Ti3Ge4 (R=Dy, Ho and Er) compounds

      R Nirmala V Sankaranarayanan K Sethupathi AV Morozkin T Geethakumary Y Hariharan

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      New R2Ti3Ge4 (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm5Ge4-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.

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