| Perovskite crystals and thin films of La2/3(Ca1-xSrx)1/3MnO3 with x ranging from 0 to 1 have been prepared with solid state reaction and RF magnetron sputtering method, investigated by various techniques:XRD analysis, resistivity in low temperature scope, magnetoresistance, cw laser and modulated laser pulse induced resistivity changing, etc.Experiments phenomena show that the properties of these materials are related with the Ca and Sr double doping level greatly, especially in photoelectrical characteristics. All samples exhibit phase transition (FM-PM) when temperature of them is increased. It is showed that the maximum of photoinduced resistivity changing ratio (ΔR/Ropt)max and its appearing temperature respectively decreases and increases when the doping level x changes from 0 to 2/3. (Δ R/Ropt)max reaches 43.5% when x is 1 ,which is an exciting figure in this research field. Experiment results show that ( ΔR/Ropt)max is strongly dependent on bias current and temperature, and the relationship among them shows a nonlinear behavior. What is more,there exists an optimal bias current and temperature condition for optical response in La2/3Ca1/3MnO3 thin film.The results of our experiments suggest that there maybe exist a common mechanism in resistivity-temperature property, CMR effect and photoinduced effect: the state of down spin eg carriers in spin order system. |
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