Characteristics of La_0.7Ca_0.3MnO₃ Powders Prepared by the Solution Combustion and Solid State Reaction Methods for Colossal Magnetoresistance Applications

Abstract

La_0.7Ca_0.3MnO₃ powders were prepared by both the solution combustion method and the solid state reaction method and were calcinated at various calcination temperatures and time intervals in air atmosphere. In the solid state reaction method, single-phase La_0.7Ca_0.3MnO₃ was obtained after heat treatment of the powder at 1000°C for 24 hr. In the solution combustion method, however, single-phase La_0.7Ca_0.3MnO₃ powder could be obtained easily when the powder was heat-treated at 650°C for only 30 min. Polycrystalline La_0.7Ca_0.3MnO₃ powder, using the solution combustion method, showed good powder characteristics, such as an average grain size of 50 nm and a specific surface area of 92 m²/g. The resistance as a function of temperature and the magnetoresistance ratio in La_0.7Ca_0.3MnO₃ thin films were attempted to examine the colossal magnetoresistance characteristics. These thin films also showed excellent colossal magnetoresistance properties in that 96% of the maximum magnetoresistance ratio was obtained at 97K.