Robust temperature coefficient of resistance of polycrystalline La0.6Ca0.4MnO3 under magnetic fields at room temperature

In the presence of magnetic field , reducing the loss in temperature coefficient of resistance ( TCR ) and increasing metal−insulator transition point ( T MI ) to room temperature are the most important concerns for the application of perovskite manganites in high−precision thermistors . Based on emerging evidence, relevant factor to address these problems lies in the interaction between Jahn−Teller (JT) distortion and magnetic field, which results in spin−orbital coupling (SOC) effect and significantly influences TCR and T MI . In this work, we studied the magnetic field induced SOC effect in polycrystalline La 1− x Ca x MnO 3 ( x  = 0.225–0.45) materials synthesized via sol−gel technique. Compounds undergo the JT distortions with increasing Ca dopant content, and the most pronounced distortion of 0.0144 at x  = 0.40 is correlated with a basal−plane distortion mode. All samples exhibit T MI values between 262 K and 288 K, indicating the enhancement of doping−induced double−exchange interaction. In the magnetic field of 1 T, SOC effect sufficiently suppresses the deterioration of TCR caused by deficient magnetization in La 0.6 Ca 0.4 MnO 3 to a value of 2.9%·K −1  at room temperature (287 K).