La_(0.82)Te_(0.18)MnO_3薄膜的庞磁电阻效应及光诱导特性

CMR Effect and the Photo-Induced Properties in La_(0.82)Te_(0.18)MnO_3 Thin Film

用脉冲激光沉积(PLD)法在LaAlO3单晶衬底上制备了VIA族非金属元素Te掺杂的La0.82Te0.18MnO3(LTMO)薄膜。X射线衍射分析表明,薄膜具有钙钛矿赝立方结构,且沿(012)方向择优生长;电阻-温度关系显示,该材料存在金属-绝缘体转变特性和庞磁电阻(CMR)效应;在0.7T的磁场作用下,薄膜的磁电阻最大值为30.6%,对应的温度在263K。而室温(303K)磁电阻值为4.8%;拟合分析表明,薄膜在低温区是单磁子散射,在高温区满足小极化子输运模型。在波长为532nm的绿激光作用下,在253K,光致电阻变化率达到最大值33.6%;分析认为这可能是由于光激发会改变材料中的磁有序,减弱双交换作用,进而改变电子的输运性质。

Using pulsed laser deposition method, the La0.82Te0.18MnO3 thin film was prepared on LaAlO3 （012） single crystal substrate. The structure of the film studied by X-ray diffractometry shows that the film has perovskite pseudocubic structure, and is of preferential orientation （012）. The R-T curves show the metal-insulator transition （MIT） and CMR effect. And the TMI are 283 K and 303 K for 0 T and 0.7 T, respectively, and they are both near room temperature. The maximum MR is 30.6% at 0.7 T. Correspondingly, the peak temperature at the maximum MR is 263 K. This shows that the films display CMR effect in the mental region. Moreover, the magnetoresistance ratio at the room temperature （303 K） is 4.8% at 0.7 T. The results show that the data satisfy R=P1＋P2T^2＋P3T4.5 for T〈TMI; when T〉TMI, it is satisfied with small polaron model. The effect of the continuous wave laser （532 nm, 40 roW） on the film was also investigated. Below TMI, the resistance increased under photo inducing. Above TMI there was a decrease of the resistance. The maximum photoinduced resistance change is 33.6%. This is attributed to the change of the magnetic order in the film because of photoinducing, which might reduce the double exchange, and change electronic transport.