Low Temperature Electrical Transport in Double Layered CMR Manganite La_(1.2)Sr_(1.4)Ba_(0.4)Mn_2O_7

摘要

The electrical transport behavior and magnetoresistance (MR) of a polycrystalline double layered manganite La_(1.2)Sr_(1.4)Ba_(0.4)Mn_2O_7, synthesized by the sol-gel method, are investigated in the temperature range 4.2 K - 300 K. The sample exhibits an insulator-to-metal transition at 87 K (T_(IM)) and the spin-glass (SG)-like behavior is observed below 50 K (T_(SG)). The transport behavior is analyzed in the entire temperature range considering three different regions: paramagnetic insulating region (T T_(IM)), ferromagnetic metallic region (T_(SG) T T_(IM)) and antiferromagnetic insulating region (TT_(SG)) by fitting the temperature dependent resistivity data to the equations governing the conduction process in the respective temperature regions. The results show that the conduction at T T_(IM) follows Mott variable range hopping (VRH) process, while the two-magnon scattering process is evidenced at T_(SG) T T_(IM) which is suppressed with the applied magnetic field of 4 T. The low temperature conductivity data are also fitted with Mott VRH equation. The sample exhibits a large MR (≈45%) over a temperature range 5 K - 50 K and it shows ≈32% MR at 5 K with a magnetic field of 0.5 T.