首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3篇
  免费   0篇
  国内免费   3篇
轻工业   1篇
一般工业技术   3篇
冶金工业   2篇
  2007年   4篇
  2005年   1篇
  2002年   1篇
排序方式: 共有6条查询结果,搜索用时 0 毫秒
1
1.
The electrical and magnetic properties of bilayer manganites La1.4Sr1.6Mn1.96TE0.04O7(TE = Mn, Fe, Ti, Nb) were investigated. Doping caused obvious changes in electrical and magnetic behaviors such as decrease of insulator-metal transition and magnetic transition temperatures, increase of peak resistivity, and different magnetoresistance effect. These changes had a significant degree of correlation with the valence of doped ions. From Fe, Ti to Nb doping, the effect was doubly stronger. The results could be well understood by considering the different destructions on double-exchange interaction and different influences on lattice distortion caused by Fe, Ti and Nb doping. The temperature dependence of magnetization measured at high field showed that the influence of doping was greatest near three-dimensional magnetic transition temperature of parent phase.  相似文献   
2.
用化学方法将Cu有关的材料引入到La2/3Ca1/3MnO3颗粒表面以形成复合颗粒系统.低磁场(0.3T)下磁电阻与温度关系测量表明,伴随着Cu有关材料的引入,磁电阻图像发生了明显变化.对纯La2/3Cal/3MnO3颗粒系统,磁电阻随温度降低而单调增加;而对复合颗粒系统,磁电阻最明显的特征是绝缘体-金属转变温度附近表现出尖的磁电阻峰,且有较高的磁电阻值.结合低场磁化实验对实验结果进行了讨论.  相似文献   
3.
用两步法制备了(1-x)La2/3Ca1/3MnO3/xSb2O5复合样品.零场下电阻温度关系测量表明,对x〈3%范围。随Sb2O5含量增加,复合样品电阻率增大,绝缘体一金属转变温度降低;而对x〉3%范围,随Sb2O5含量增加。复合样品电阻率减小,绝缘体一金属转变温度提高.磁电阻测量表明,少量Sb2O5同La,2/3C&1/3MnO3复合,可明显增强磁电阻效应.  相似文献   
4.
Samples with nominal composition of (1 - x)La0.67Ca0.33MnO3 (LCMO)/xCuO (x = 0%, 2%, 4% and 20% ) were made using a special experimental method. The temperature dependence of the resistivity (ρ) of the composites was investigated in the temperature range of 10 - 300 K and different magnetic fields of H = 0, 0.1, 0.3, 0.5, 1.0 and 3.0 T. The results showed that CuO percentage x had important effects on metal-insulator transition temperature (Tp), zero field peak resistivity (ρmax), and magnetoresistance (MR) properties of the composites. Tp shifted sharply towards low temperature with the increase of x in the range of x ≤4%, but was almost independent of x at high level of CuO content. Composites with x = 4 % and 20 % exhibited similar electrical transmission behavior. Compared with pure LCMO, enhanced magnetoresistance could be clearly observed even in a quite low magnetic field of 0.3 T. For x =4% and 20% samples, the MR value at 0.3 T could reach as high as - 88% and - 90%, respectively. XRD and SEM analysis showed that the substantial enhancement of MR, especially near Tp, was because of local spin disorder between contiguous LCMO ferromagnetic particles caused by the addition of CuO.  相似文献   
5.
纳米TiO2的多相光催化应用研究进展   总被引:7,自引:0,他引:7  
纳米TiO2在紫外光的照射下可激发产生电子空穴对,从而引发一系列有意义的氧化还原反应。利用该特性,纳米TiO2可用于降解结构稳定的有机和无机化合物、杀灭微生物和肿瘤细胞、制备特殊功能的催化剂以及回收贵重金属等。目前该领域的研究大多停留在实验室水平,机理分析推测多,反应中间体鉴定少,其理论探讨和实际应用还有许多工作要做。  相似文献   
6.
用化学方法制备了(1-x)La0.67Ca0.33MnO3(LCMO)/xMgO颗粒复合体系.通过选择不同的前期预烧温度(Ts1)控制LCMO原粉的颗粒大小.研究表明,MgO的含量和LCMO的前期预烧温度对复合体系的电输运和磁电阻效应有显著的影响.对瓦1=1100℃的样品,仅在纯LCMO和x=1mol%的复合样品中可以观察到绝缘体金属转变.而对Ts1=900℃的样品,在x=7mol%的复合样品中还可以观察到绝缘体金属转变,其最大低场磁电阻(H=0.3T)从纯LCMO的5%增加到27%.SEM形貌分析表明MgO含量增加或LCMO前期预烧温度升高都使复合体系中LCMO颗粒之间的联结性减弱.运用自旋极化隧穿机理,对实验结果进行了讨论.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号