Investigation of magneto-transport properties of the co-doped La1.6-xPrxCa1.4-xBaxMn2O7 (x=0.2 and 0.4) double-layered manganite

Structural and magneto-electrical transport properties of double-layered La1.6-xPrxCa1.4-xBaxMn2O7 (x = 0.2 and 0.4) manganite compounds were studied. X-ray diffraction patterns refinement shows that the samples crystallize in a tetragonal I4/mmm structure, whereas a rhombohedral structure phase with R-3-c space group is detected as a secondary phase. The electrical resistivity under 0 and 1 T exhibited a metal-insulator transition at T-MI. It is found that the rho(T) decreases with increasing Pr-Ba contents. Magnetoresistance (MR%) curves displayed a maximum value of similar to 51.69% at 63 K for the x = 0.2 sample and decreases with increasing Pr-Ba concentrations to similar to 33.44% at 64 K for x = 0.4 under 1 T. The obtained values of the temperature coefficient of resistivity for both samples have similar trend as T-MI. Below T-MI,T- rho(T = rho(0) - rho T-0.5(0.5) + rho T-2(2) + rho T-5(5) model fits well the resistivity curves which reflect a combination of the grain boundary effects, weak localization, electron-electron, and electron-phonon scattering to the electrical resistivity. Above T-MI, the non-adiabatic small polaron hopping model describes the electrical resistivity behavior in T > theta(D)/2 region. The Mott's 3D variable range hopping mechanism (3D-VRH) was found to be the most suitable mechanism for describing the high-temperature resistivity behavior between T-MI and theta(D)/2. The density of states near the Fermi level N(E-F) and mean hopping energy (E-h) of the charge carriers have been calculated from the experimental curves using Mott's 3D-VRH model. The experimental and fitting curves of the resistivity and the related results are discussed in detail.