稀土锰氧化物La_(0.7)Ca_(0.3)Mn_(1-x)Cu_xO_3低场磁电阻及电传输特性研究  

Low-Field Magnetoresistance and Electrical Conductivity Properties for Perovskite Manganite La_(0.7)Ca_(0.3)Mn_(1-x)Cu_xO_3

作　　者：张洪[1] 刘银春[1] 黄志高[2] 

机构地区：[1]福建农林大学机电工程学院,福州福建350002 [2]福建师范大学物理与光电信息科技学院,福州福建350007

出　　处：《中国稀土学报》2007年第6期724-729,共6页Journal of the Chinese Society of Rare Earths

基　　金：福建省自然科学基金重点资助项目(E0320002);福建农林大学青年教师科研基金项目(07B29)

摘　　要：采用溶胶-凝胶法制备了系列多晶CMR材料La0.7Ca0.3Mn1-xCuxO3（x=0%,1%,5%,10%,15%,20%）。在77-350 K温度范围内测量了样品的电阻率及磁电阻大小。实验结果发现：系列样品TC随掺杂量增加而递减;系列样品的电阻率峰及磁电阻峰在整个测温范围内随掺杂量的增加均依次被展宽直至消失,当掺杂量为x≥10%时,电阻率随温度的变化在整个测温范围内呈现绝缘相行为;同时还发现,掺杂量为x≥10%时,样品的磁电阻在整个测温区内基本表现为隧穿磁电阻。基于我们采用蒙特卡罗模拟方法提出的逾渗模型及隧穿磁电阻模型,对样品的磁电阻行为进行了很好的解释。对系列样品的ρ-T曲线进行lnρ-T^-（1/4）系拟合,发现掺杂量为x=10%样品在整个温区内的lnρ-T^-（1/4）系基本呈线性。A series of polycystalline bulk samples of La0.7Ca0.3Mn1-xCuxO3（x =0%, 1%, 5%, 10%, 15%, 20%） were prepared by sol-gel process. The temperature dependence of resistance and magnetoresistance （MR） for all the samples were measured from 77 K to 350 K. It was found that the Courie temperature （Tc） of samples La0.7Ca0.3Mn1-xCuxO3 decreased with increasing substitutional doping. Secondly the peaks of resistance and magnetoresistance broadened till disappeared along with increasing substitutional doping, when the content of substitutional doping exceeded 10%, the temperature dependence of resistance exhibited as insulator in the whole temperature region. Simultaneously, it was found that the MR of samples （x ≥ 10% ） appeared to be tunnelled MR in the whole temperature region. According to the model of spin-polarized electron tunneling and percolation, the magnetoresistance as a function of temperature was explained well. Thirdly, using the function of lnρ-T^-（1/4）, the p-T curves were fit. It was found that the function of lnρ-T^-（1/4） of the sample x = 10% appeared to be linear in the whole temperature region.

关 键 词：磁电阻 溶胶-凝胶 稀土锰氧化物 蒙特卡罗模拟方法 稀土 

分 类 号：O482.5[理学—固体物理]