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    Infrared and Structural Properties of Y1-xNdxBa2Cu3O7-? (0 < x < 1)
    (2002) Adigüzel H.I.; Izgi T.
    Infrared and structural properties of Y1-xNdxBa2Cu3O7-? (0 < x < 1) were investigated using infrared absorption spectroscopy and X-ray powder diffraction. The unit cell parameters of the samples were defined using X-ray diffraction data. The resistance measurements showed that the samples revealed superconductivity in the temperature range of 80-100 K. It was observed that by the substitution of Nd to Y in YBa2Cu3O7-? IR band at 573 cm-1 that is assigned as Cu-O axial antisymmetric stretching mode shifts to 533 cm-1 while the band at 620 cm-1 that is due to Cu-O symmetric stretching mode in YBa2Cu3O7-? shifts to 588 cm-1. ©2002 Plenum Publishing Corporation.
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    Magnetotransport and magnetoresistance properties of Pr 0.68Ca0.32-xSrxMnO3 (x= 0, 0.1, 0.18, 0.26 and 0.32) manganites
    (National Institute of Optoelectronics, 2011) Izgi T.; Kolat V.S.; Bayri N.; Kaya A.O.; Gencer H.; Atalay S.
    In this study, the magnetotransport and magnetoresistance properties of Pr0.68Ca0.32-xSrxMnO3 (x= 0, 0.1, 0.18, 0.26 and 0.32) compounds were investigated. The system illustrate an evolution from a charge-ordered manganite at x = 0, with an insulating-like resistivity and low magnetization values, towards to a completely ferromagnetic metallic state for x = 0.32. Above the metal-insulator transition temperature TMI, the resistance curves were fitted to the small polaron popping model. The activation energy (Ea) was found to decrease with increasing Sr content. In the phase separated (PS) state, due to the coexistence of ferromagnetic (FM) metallic and charge order (CO) insulating phases, the magnetoresistance (MR) was found to be maximum. The MR ratio of 6.3x10 8 for the sample x = 0 at 60 K is one of the largest MR change has been reported in manganites. The MR values decreases considerably with increasing Sr content and the activation energy decreases with the increase of Sr content.