Structural, Magneto Transport And Magnetic Properties Of Ruddlesden-Popper La2-2xsr1+2xmn2o7 (0.42 <= X <= 0.52) Layered Manganites

The magneto transport of Ruddlesden-Popper, La2-2xSr1+2xMn2O7 (0.42 <= x <= 0.52), 2-dimensional bilayered manganites have been investigated in a broad temperature range. The samples have been synthesized using the solid-state reaction method. Rietveld refinement of the X-ray diffraction data indicates the tetragonal structure formation with I4/mmm space group. The resistivity curves of the samples present a general characteristic of metal-insulator (MI) transition at certain temperature (T-MI). Besides, for samples with x = 0.48, 0.50, and 0.52, at a certain temperature (T-CO) well below T-MI the charge ordering is also evident. Furthermore, the samples display a shallow upturn in resistivity below T-min due to the Kondo like spin scattering effect, weak localization and electron-phonon interaction. The high temperature semiconducting (T>T-MI) region, the resistivity curve follows the 3D Mott's variable hopping transport mechanism. The overall suppression of resistivity accounts for a substantial magnetoresistance by applying a magnetic field and the characteristic change in T-MI, T-CO, and T-min are discussed. Temperature-dependent magnetization demonstrates the suppression of ferromagnetism and evident of antiferromagnetic nature with an apparent charge ordering with increasing concentration of Sr2+.