Adjusting the K-doping of La1-xKxMnO3 (0.1 ≤ x ≤ 0.35) films to obtain high TCR and LFMR at room-temperature

Abstract

Compared with conventional thermal and magnetic sensing materials, perovskite manganese oxide films with a rapid shift from ferromagnetic metals to paramagnetic insulators can be more suitable for the fabrication of uncooled infrared bolometers and magnetic sensors. However, the main challenge is to obtain perovskite manganese oxide films with high temperature coefficient of resistivity (TCR) and low field magnetoresistance (LFMR) at room temperature. In this study, La1-xKxMnO3 (LKMO, 0.10 ≤ x ≤ 0.35) films with different K-dopant amounts were prepared on SrTiO3 substrates using sol–gel spin coating method. A comprehensive analysis of their structure, morphology, and ionic valence enabled one to conclude that varying K-dopant content from 0.10 to 0.30 caused a decrease in Mn-O bond lengths and an increase in Mn-O-Mn bond angles, as well as caused the grain growth and the rise in Mn4+ content in LKMO films. All these changes resulted in a significant alteration in the resistivity of LKMO films, thereby providing the larger TCR and LFMR values at room temperature. According to the results, La0.7K0.3MnO3 with 13.13 % K−1TCR and La0.85K0.15MnO3 with 46.39% LFMR (under an external magnetic field of 1 T) are promising materials for the manufacturing of uncooled infrared bolometers and magnetic sensors, respectively.