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.
出处
《中国稀土学报》
CAS
CSCD
北大核心
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)
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
inorganics non-metallic materials
composite system
colossal magnetoresistance
interfacial tunneling
low-field magnetoresistance
rare earths
