Synthesis, Characterization and Magnetotransport Behavior of La-Based Double Layered Manganites

Y.S. Reddy Department of Physics, Chaitanya Bharathi Institute of Technology (A), Hyderabad 500 075, Telangana State, India

Received: December 4, 2016; Revised version: May 15, 2017; In final form: May 18, 2017

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The single phase double layered manganites La1.2Sr1.8-xCaxMn2O7 (x=0.0, 0.3) were synthesized by the sol-gel method. The electrical resistivity at various magnetic fields over a temperature range 4.2-300 K was measured. The insulator-to-metal transition temperature (TIM) decreases from 123 K (x=0.0) to 70 K (x=0.3). The spin-glass (SG)-like transition is observed in both the samples at 30 K (TSG - SG-like transition temperature). The transport behavior is analyzed in the entire temperature range (4.2-300 K) in three different regions: paramagnetic insulating region (T>TIM), ferromagnetic metallic region (TSG<T<TIM) and antiferromagnetic insulating region (T<TSG) by fitting the equations governing the conduction process to the temperature dependent resistivity data in different temperature regions. The results indicate that the Mott variable range hopping (VRH) dominates the transport behavior at T>TIM in the two samples. At TSG<T<TIM, the conduction follows the Zener polynomial law ρ=ρ0+ρ2T2+ρ4.5T4.5 which suggests the contribution of two-magnon scattering process to the conduction. The zero field conductivity at T<TSG obeys T1/2 dependence, consistent with weak localization effects.

DOI: 10.12693/APhysPolA.131.1544 PACS/topics: double layered manganites, electrical transport, magnetoresistance, variable range hopping, spin-glass-like behavior, magnon scattering