Abstract
A crossover from positive to negative persistent photoconductivity (PPC) has been observed in the thermal hysteresis region of a La0.325Pr0.3Ca0.375MnO3 thin film. In the cooling process, the resistance shows downward relaxation in darkness. Light illumination induces a resistance drop and positive PPC is observed. However, upon warming, the resistance exhibits upward relaxation without illumination. Moreover, the response of the film to light illumination shows distinct behavior. The resistance decreases to a lower value when the illumination is switched on and then shows upward relaxation during illumination. It recovers to a higher value when the illumination is stopped, which characterizes negative PPC. The PPC ratio is −30.2% at 125 K with a light intensity of 3.06 mW mm−2. These results are discussed based on the phase competition and phase stability switch between ferromagnetic metal and charge/orbital-ordered insulator states. The results may be important for practical applications in photoelectric devices.
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