【摘 要】
：
Nanoscale layered-perovskite La2.5-xK0.5+xMn2O7 (0 ＜ x ＜ 0.5) have been prepared by the modified sol-gel method, and their structural, magnetic and electric prope
【机 构】
：
National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093“,”Key Laborat
论文部分内容阅读
Nanoscale layered-perovskite La2.5-xK0.5+xMn2O7 (0 ＜ x ＜ 0.5) have been prepared by the modified sol-gel method, and their structural, magnetic and electric properties have been studied. The experimental results show that these materials exhibit paramagnetic-to-ferromagnetic phase transitions at 183, 216, 230, 238 and 249K for x = 0.05, 0.15, 0.25, 0.35 and 0.45, respectively. For all compositions of La2.5-xK0.5+xMn2O7 investigated here, we have observed no metal-nonmetal transition phenomena for the whole temperature region (80 - 300 K).The nanoscale samples exhibit highly enhanced magnetoresistance (MR) effects especially at low temperatures (＜ Tc). The MR behaviour can be explained by taking into account the two-dimensionality with anisotropy of the Mn-O networks and nanoscale grain size effect in the layered manganese perovskites.
其他文献
甾体性腺激素的异常分泌是导致子宫腺肌病（ＡＭ）的重要原因 ,其中泌乳素在ＡＭ的发生中有重要作用。本文探讨了子宫腺肌病患者的泌乳素分泌状态和可能的临床意义。对象和方法选择１９９７年７月～１９９９年
The phenomena of improved edge confinement due to ion cyclotron radio frequency boronization were observed with a fast reciprocating Langmuir probe in the HT-7
CNx films with x ≈ 0.5 were prepared on to a titanium coated ceramic substrate by using microwave plasma enhanced chemical vapour deposition. As-deposited film
A model is proposed to describe the photoelectron decay process at room temperature in cubic AgCl microcrystals homogeneously doped with K4Fe(CN)6. By combining
By analysing the action of a beamsplitter on squeezed vacuum states (SVSs), it is found that, if the two inputlight beams of the beamsplitter have the same sque
贵刊2011年12期“万新有约”栏目中《侠商刘大伟:行业责任的守望者》一文问给我留下了深刻印象,刘大伟在经营好自己企业的同时,身体力行,以自己的影响力极力维护行业生态环境
利用云南高秆大穗大粒品种“毫糯干相”与“IR_(29)”品种杂交育成了两个中矮秆、优质、大粒的水稻新品系—“云香糯一号”和“云香糯25号”。在云南、广西、四川等省的一些
本试验采用C0~(60)γ-射线1.2万伦照射龙辐73-8955大豆(Glycine Max. (L.)Merr)稳定系的风干种子,于干燥器中贮存不同时间,以探明辐射的贮存效果。研究表明,贮存对M_1—M_3的
The principle of charge transfer agents was investigated experimentally. There is a compensation effect betweentriethanolamine (TEA) and diphenyliodonium hexafl
In the framework of the Glauber model, taking into account the energy loss of the beam proton through the nucleus, we analyse the measured Drell-Yan production