• Sugata Ray

      Articles written in Journal of Chemical Sciences

    • Properties of a new magnetic material: Sr2FeMoO6

      D D Sarma Sugata Ray

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      Recently, there have been a large number of investigations of the physical properties of Sr2FeMoO6 and related compounds, in view of their significant negative magnetoresistive property at room temperature and in low applied magnetic fields. We review these investigations, detailing the microscopic mechanism controlling the electronic and magnetic properties of this system.

    • Electron spectroscopic investigation of metal-insulator transition in Ce1-xSrxTiO3

      U Manju S R Krishnakumar Sugata Ray S Raj M Onoda C Carbone D D Sarma

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      We have carried out detailed electron spectroscopic investigation of Ce1−x SrxTiO3 exhibiting insulator-metal transition withx. Core level X-ray photoelectron spectra of Ce3d as well as resonant photoemission spectra obtained at the Ce4d→4f resonant absorption threshold establish Ce as being in the trivalent state throughout the series. Using the ’off-resonance’ condition for Ce 4f states, we obtain the Ti3d dominated spectral features close toEF, exhibiting clear signatures of coherent and incoherent peaks. We discuss the implications of our findings in relation to the metalinsulator transition observed in this series of compounds.

    • A microspectroscopic study of the electronic homogeneity of ordered and disordered Sr2FeMoO6

      Dinesh Topwal U Manju Sugata Ray S Raj D D Sarma S R Krishnakumar M Bertolo S La Rosa G Cautero

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      Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with composition fluctuations of the type Sr2Fe1+xMo1-xO6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions.

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