Transport properties and colossal magnetoresistance in epitaxial La_0.67Cd_0.33MnO₃ thin film

Abstract

An optimal composition of La_0.67Cd_0.33MnO₃ was synthesized by ceramic route. The compound crystallized in a rhombohedral structure with lattice parameters a=5.473(4)Å and α=60°37'. Resistivity measurement showed an insulator-to-metal transition coupled with a ferromagnetic transition of around 255 K. Epitaxial thin films were fabricated on the LaAlO3 (100) substrate by a pulsed laser deposition technique. The psuedocubic lattice parameter a of the film is 3.873(4) Å. The insulator-to-metal transition of the film was observed at 250 K which is comparable with the bulk value. The film was ferromagnetic below this temperature. Magnetoresistance defined as ΔR/R₀=(R_H-R₀)/R₀ was over-86% near the insulator-to-metal transition temperature of 240 K at 6 T magnetic field and over-30% at relatively low fields of 1 T. No magnetoresistance was observed at low temperatures in the film unlike in the polycrystalline sample, where about a 40% decrease in resistance was observed on applying 6 T magnetic field due to the spin dependent scattering at the grain boundaries.