Low-temperature magnetotransport properties in granular ferromagnetic manganites

ECMP Division, Saha Institute of Nuclear Physics - 1/AF, Bidhannagar, Kolkata 700 064, India

Corresponding author: soumik.mukhopadhyay@saha.ac.in

Received: 18 April 2007
Accepted: 23 July 2007

Abstract

The magnetotransport properties at low temperature in La_0.67Sr_0.33MnO₃ nanoparticles, La_0.67Sr_0.33MnO₃/Al₂O₃ nanocomposites and ferromagnetic-manganite thick films have been studied. All the samples exhibit low-temperature upturn in resistivity and enhanced low-field magnetoresistance of varying magnitude below the resistivity minima. The voltage dependence of conductance at low temperature for all the samples can be described by a universal scaling function , where the scaling parameter V₀ is sensitive to the magnetic field. The observed magnetotransport properties are explained in a unified treatment incorporating both inter-grain tunneling conduction and thermal activation over the inter-grain potential barrier lowered by the electric field.