中文摘要：

采用传统固相反应法制备了双层钙钛矿结构锰氧化物La1.8Ca1.2Mn2O7陶瓷,并用X射线粉末衍射法,扫描电镜,HL5500PCHall效应分析仪和综合物性测量系统（PPMS）对其磁、电性质进行了表征.结果表明：经过两次高温烧结可合成具有双层Sr3Ti2O7型四方结构的La1.8Ca1.2Mn2O7陶瓷,且晶格常数a和b为3.901（1=0.1nm）,c为19.369,晶胞体积为295.213,Curie温度TC为177K.当温度低于Curie点177K时,I-V出现非线性,温度越低,非线性行为越明显;T=14K时非线性系数α为68.6;而当温度高于样品Curie点时,非线性现象消失.表明样品在TC以下存在磁、电耦合并由于耦合作用产生磁性相关势垒.该势垒特性可用一对背对背的pn结势垒等效,在T=14K时,通过I-V测量,得到最大磁性结势垒值为0.18eV。

英文摘要：

The double-layered perovskite La1.8 Ca1.2 Mn2O7 ceramic was synthesized by traditional solid-state reaction after heat treatment for two times at high temperature.Its structure,magnetic and electrical properties were characterized by x ray diffraction（XRD）,scanning electron microscopy（SEM）,HL5500PC and physical properties measurement system（PPMS）.It has a double-layered Sr3Ti2O7 tetragonal structure with lattice constants a,b = 3.901（1 = 0.1 nm） and c = 19.369 ,and unit cell volume V = 295.21 3.The Curie temperature TC is 177 K.The I-V characteristic shows a nonlinearity increasing with decreasing temperature at low temperatures below the magnetic critical point of TC and the nonlinear coefficient α goes up to a maximum of 68.6 when the temperature goes down to the lowest of 14 K in this experiment.However,the nonlinearity disappears when temperature goes above the magnetic transition point of TC.It indicates that a magnetically correlated Schottky barrier between grain boundaries is responsible for the I-V nonlinearity when temperature is below the Curie temperature.A maximum value of 0.18 eV was obtained for the magnetic Schottky barrier at 14 K after using a back to back pn junction model to describe such a potential barrier between grain boundaries.