Electrical transport in manganite granular systems

Abstract

A systematic investigation of magnetic and transport properties is carried out for ${\mathrm{La}}_{2/3}{\mathrm{Ca}}_{1/3}{\mathrm{MnO}}_{3}$ granular system. Based on the magnetization measurement, it is argued that oscillatory indirect magnetic exchange coupling via the boundary material with thickness s sandwiched between the neighboring grains exists in polycrystalline manganites. By introducing a distribution function of s and averaging the conductivity deduced from the spin-polarized tunneling model for the neighboring grains, we obtain a general expression for the temperature dependence of resistance that can reproduce the experimental data observed in polycrystalline manganites. The present model provides information on the microscopic transport mechanism.