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 La 1.6-x Pr x Ca 1.4-x Ba x Mn 2 O 7 (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 ρ(T) decreases with increasing Pr-Ba contents. Magnetoresistance (MR%) curves displayed a maximum value of ∼51.69% at 63 K for the x = 0.2 sample and decreases with increasing Pr-Ba concentrations 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 , ρ T = ρ 0 - ρ 0.5 T 0.5 + ρ 2 T 2 + ρ 5 T 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 > θ 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 θ D /2. The density of states near the Fermi level N ( E F ) , mean hopping distance, ( R h ) 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.