双层钙钛矿锰氧化物La_(1.34)Sr_(1.66)Mn_(2-x)Cr_xO_7的磁性和输运性质  

Magnetic and Transport Properties in Two-layered Perovskite Manganites La_(1.34)Sr_(1.66)Mn_(2-x)Cr_xO_7

作　　者：宗云[1,2,3] 赵旭[1,3] 陈伟[1,3] 

机构地区：[1]河北师范大学物理科学与信息工程学院,河北石家庄050016 [2]石家庄信息工程职业学院计算机系,河北石家庄050035 [3]河北省新型薄膜材料实验室,河北石家庄050016

出　　处：《河北师范大学学报（自然科学版）》2009年第2期198-201,共4页Journal of Hebei Normal University：Natural Science

基　　金：河北省自然科学基金(E2008000194)

摘　　要：采用固相反应法制备了双层钙钛矿结构锰氧化物La1.34Sr1.66Mn2-xCrxO7（x=0,0.1,0.2,0.3,0.4）多晶系列样品,XRD分析表明,所有样品均为Sr3Ti2O7型四方结构,空间群为I4/mmm.随着Cr^3＋离子掺杂浓度的增加,该系列样品的晶胞体积单调减小.对于少量Cr^3＋离子掺杂的样品（x=0.1）,三维长程铁磁有序转变温度T3cD升高,二维短程铁磁有序转变温度T2cD降低;结构分析表明,x=0.1样品的晶格常数c最小,a最大,c/a达到极小值;样品中严重的晶格畸变导致双交换作用强度的改变是其磁有序转变温度变化的主要原因.对于大量Cr^3＋离子掺杂的样品（x=0.3,0.4）,T3cD降低,Tc2D基本保持不变.样品在150～300 K范围内电阻率随着温度的降低单调增加,显示出绝缘体或半导体行为,并且随着Cr离子的掺杂电阻率单调增加.The two-layered perovskite manganites La1.34Sr1.66Mn2-xCrxO7（x=0,0.1,0.3,0.4） were prepared by a standard solid-state reaction method.The XRD patterns indicate that all samples can be indexed to a tetragonal Sr3Ti2O7 type sturcture with a space group I4/mmm.The cell volume V of the samples decreases monotonically with increasing Cr^3＋ ion concentration.For lightly Cr^3＋ doped sample（x=0.1）,the three-dimensional long-range ordering ferromagnetic transition temperature T3Dc increases,while the two-dimensional short-range ordering ferromagnetic transition temperature T2Dc decreases.A minimum of the c parameter,a maximum of the a parameters and a minimum of the c/a ratio were found in the x=0.1 sample.The change of the double-exchange-interaction resulting from the serious lattice distortion is the main cause of the variation of the magnetic ordering transition temperatures in this sample.For the heavily Cr^3＋doped samples（x=0.3,and 0.4）,T3Dc decreases,but T2Dc almost remains stable.The resistivity increases with decreasing temperature in the range of 150～300 K,showing a insulating or semiconductor behaviour.The resistivity increases monotonically with increasing Cr^3＋ doping level.

关 键 词：固相反应法 双层钙钛矿锰氧化物 磁特性 

分 类 号：O484.43[理学—固体物理] TB61[理学—物理]