Research on a New Process of Preparation for Nano-SiO2 with High Activity and Mesopores
Research on a New Process of Preparation for Nano-SiO_2 with High Activity and Mesopores

With substitution of La by Tb in (La1-xTbx)0.67Sr0.33MnO3, the room temperature magnetoresistance AR/R0 drops at first, then undergoes an increase near x≈0.1, and finally drops again. The value of room temperature magnetoresistance at a field H=12 kOe for (La0.9Tb0.1)0.67Sr0.33MnO3 is -3.56%. The enhancement of the room temperature magnetoresistance induced by an appropriate Tb substitution in (La1-xTbx)0.67Sr0.33MnO3 is correlated with the shifts of the Curie temperature and metal-insulator temperature to near room temperature. The drop of the room temperature magnetoresistance at large Tb doping-contents may be due to its lower TC and TMI far from the room temperature.