(La_(0.67)Ca_(0.33)MnO_3)_x/(ZrO_2)_(1-x)复合体系的磁性和传输特性  

Magnetic and Magnetoresistance Properties in (La_(0.67)Ca_(0.33)MnO_3)_x/(ZrO_2)_(1-x) Composite System

作　　者：黄宝歆[1] 刘宜华[1] 张汝贞[1] 原晓波[1] 王成建[1] 郝小鹏[1] 

机构地区：[1]山东大学物理学院和晶体材料国家重点实验室

出　　处：《中国稀土学报》2004年第6期755-759,共5页Journal of the Chinese Society of Rare Earths

基　　金：国家重点基础研究专项经费资助项目(G1998061310)

摘　　要：将用溶胶 凝胶法得到的La0.67Ca0.33MnO3(LCMO)微粉与ZrO2的颗粒进行复合,制备了(LCMO)x/(ZrO2)1-x渗流复合体系。当LCMO的体积分数为40%时,复合体系达到渗流阈值,此时材料在低温下的磁电阻得到显著增强。77K时在10mT的磁场下,(LCMO)0.4/(ZrO2)0.6的磁电阻比为7.8%,相对于LCMO增加了712%。低场磁电阻(LFMR)的增强是由于载流子在二者界面处发生的自旋相关隧穿效应。由于界面反应,不可避免地产生了Zr离子对Mn离子的B位替代,从而引起材料磁性M和居里温度TC的下降。在x<60%时,TC保持在220K附近基本不变,说明该B位替代是有限的。The (La_(0.67)Ca_(0.33)MnO_3)_x/(ZrO_2)_(1-x) (x is the volume fraction ratio) percolated composites were fabricated by combining La_(0.67)Ca_(0.33)MnO_3 (LCMO) powders with ZrO_2 particles, where the LCMO powders were prepared by sol-gel process. The low field magnetoresistance (LFMR) is greatly enhanced at low temperature when the system is close to the metallic percolation threshold of x=0.4. The magnetoresistance ratio of (LCMO)_(0.4)/(ZrO_2)_(0.6) in a 10 mT magnetic field at 77 K is 7.8%, about by 712% larger than that of the pure LCMO compound. The enhancement of the spin-dependent tunneling of the electrons at the interfaces of LCMO and ZrO_2 grains is responsible for the enhanced LFMR. With increasing ZrO_2 addition, the Curie temperature T_C decreases firstly and then remains a constant at about 220 K when x<60%, showing the limited substitution effect of Zr ions on the B sites.

关 键 词：无机非金属材料 复合体系 庞磁电阻 界面隧穿 低场磁电阻 稀土 

分 类 号：O482[理学—固体物理] TB34[理学—物理]