Magneto-resistance enhancement due to self-hole-doping in LaMnO3 produced by low temperature heat treatment

Abstract

We have observed the magneto-resistance (MR) enhancement due to the self-hole-doping (SHD) in LaMnO3 (LMO) produced by low temperature heat treatment (LTHT). The polycrystalline LMO samples were prepared by solid-state-reaction. After the calcination at 1100°C for 18 hours under oxygen gas flow (OGF) and grinding, the powders were pressed into pellets and were sintered at 1100°C and 1300°C for 18 hours under the OGF Although the single crystal of LMO is an insulator, the polycrystalline LMO samples showed large electrical conduction due to the SHD and especially the sample sintered at 1100°C indicated the metallic conduction. We consider that by the sintering in sufficient oxygen gas atmosphere, excess oxygen was mainly introduced into the amorphous-like grain boundary regions (AGBRs) and the high SHD was caused. The LTHT generated large AGBRs in the LMO samples and the MR enhancement was observed.