【摘要】 利用溶胶—凝胶法制备了(La_0.7Sr_0.3MnO₃)_（1-x）（CoFe₂O₄）_x复合体材料,并利用X射线衍射和⁵⁷Fe的穆斯堡尔谱详细研究了其结构和微结构.利用超导量子磁强计测量了样品的磁性.结构和磁性的测量表明(La_0.7Sr_0.3MnO₃)_（1-x）（CoFe₂O₄）_x复合体由La_0.7Sr_0.3MnO₃和CoFe₂O₄组成,两相之间没有反应.复合体的电阻率随着CoFe₂O₄的加入而逐渐升高.在室温条件下5kOe的磁场下得到了-5%的磁电阻效应,该值比同样晶粒大小的纯La_0.7Sr_0.3MnO₃样品的磁电阻效应大一倍.同时也比将非磁性的绝缘势垒如玻璃、CeO₂等引入La_0.7Sr_0.3MnO₃的室温磁电阻值大.表明一定量的铁磁性绝缘势垒的引入可以增强类钙钛矿锰氧化物的室温磁电阻效应.更多还原

【Abstract】 (La_0.7Sr_0.3MnO₃)_（1-x）（CoFe₂O₄）_x composites were fabricated by the sol-gel method.X-ray diffraction,M（?）ssbauer spectroscopy,SQUID and resistivity measurements were used to investigate the struc- ture,microstructure,magnetic properties and magnetoresistance（R_M）effect of the samples.The resistivity of (La_0.7Sr_0.3MnO₃)_（1-x）（CoFe₂O₄）_x increases with the increase of x.The magnetoresistance（-5%）is about two times larger than that of the same-grain-sized La_0.7Sr_0.3MnO₃ sample in the field of 5 kOe at room temperature.Our results indicate that the magnetoresistance effect can be enhanced by introducing ferro- magnetic barrier in perovskite manganites.更多还原