【摘要】 研究层状钙钛矿结构锰氧化物 La1 .2 Ca1 .8Mn2 - x Tix O7( x=0 .0 0 ,0 .0 5,0 .1 0 )块状样品磁电阻性质 ,发现 Mn位掺杂 Ti4+ 离子使材料电阻率上升 ,电阻率峰值温度 Tp 降低 ,Tp 附近及低温下磁阻增加 ;当 x=0 .1 0时 ,材料在所测温区表现为类绝缘态 ,但在 H=0 .5T外场下可观察到场致的金属 -绝缘体转变 ,同时获得磁电阻 ( MR=〔ρ( H) -ρ( 0 )〕/ρ( 0 ) )高达 -4 3 %。对以上结果的解释应是同时考虑在层状钙钛矿材料内的各向异性交换作用和因磁结构被破坏而产生的具有不同磁相关长度的区域的共存更多还原

【Abstract】 The properties of magnetoresistance of the layered perovskite manganite La 1.2 Ca 1.8 Mn 2-x Ti xO 7(x=0.00,0.05,0.10)have been studied.The doping of Ti 4+ ion at manganese site exhibits an increase in resistivity,a decrease in the resistivity peak temperature and an enhancement of the magnetoresistance low temperature in the compounds.When x=0.10,the system behaves insulator-like over the whole measuring temperature range,but a metal-insulator transition induced by a external field of 0.5T was observed,which causes a large magnetoresistance (MR=〔ρ(H)-ρ(0)〕/ρ(0))of-43%.The above results can be explained in terms of the anisotropic exchange interaction in layered perovskites and the coexistence of the regions with different magnetic coherence length originating from the disorder of magnetic structure.更多还原