La–Ca–Mn–O Thin Film based Thermistor for Measuring Low Temperature of 77–230 K

Perovskite manganite La–Ca–Mn–O (LCMO) thin films were deposited on LaAlO3 (001) single crystal substrate by radio-frequency magnetron sputtering at room temperature. After annealing at 800–1000°C in O2 atmosphere for 1 h, sheet resistance (R) of the LCMO thin films was measured by van der Pauw method in the range of 77–300 K. The characteristic resistance-temperature curves of all the annealed films showed typical insulator to metal transition behavior of colossal magnetoresistance (CMR) materials on cooling. The sheet resistance of LCMO films changes with temperature, conforming to a function of exp (βT) in the temperature range from 77 K to 230 K, which is applicable to an oxide thin film thermistor.