共查询到19条相似文献,搜索用时 140 毫秒
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制备了结构为 ITO/CuPc/NPB/Alq3/LiF/Al 的有机发光二极管,并在300,260,220和180 K 四个温度测量了器件在恒压偏置下注入电流的磁场效应(磁电导效应).在注入电流从双极电流过渡到单极电流的过程中,随电流减小,器件的磁电导呈现先上升后下降的变化趋势.当温度降低,磁电导的值下降.但在任何测量条件下,器件的磁电导始终为正,没有出现如文献报道的磁电导从正到负的变化.实验结果表明,有机发光二极管中正负磁电导现象的产生,并非仅取决于注入电流是单极电流还是双极电流,它还与有机材料、器件结构等密切相关.利用受磁场调控的“电子-空穴对”机理与“双极化子”模型,分别解释了器件双极电流和单极电流的正磁电导效应.
关键词:
有机发光二极管
磁电导
双极化子 相似文献
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一种新的庞磁电阻氧化物薄膜La1-xPrxMnO3(x=0.1,0 .2)薄膜用脉冲激光沉积(PLD)方法生长在(100)SrTiO3单晶基底上.XRD结果显示 薄膜具有很好的外延单晶取向.电输运和磁性质的研究表明薄膜具有显著的庞磁电阻效应(CM R)效应,其中磁电阻比率达95%(在5T的磁场下).X射线光电子能谱(XPS)的结果表明薄膜体 系中Pr离子的价态为+4价,因此该薄膜很可能是电子掺杂的庞磁电阻体系.
关键词:
脉冲激光沉积
1-xPrxMnO3')" href="#">La1-xPrxMnO3
电子 掺杂
庞磁电阻 相似文献
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在成功制备具有双钙钛矿结构Sr2Fe1-xCoxMoO6系列样品的基础上,对其结构、输运性质和磁性质进行了系统研究.结果发现,随着Co替代浓度x值的增加,样品的电阻率-温度关系由半金属行为转变为半导体行为,其室温电阻率从3.9×10-5Ω·cm增大到6.0×10-1Ω·cm;样品由亚铁磁体转变成反铁磁体,其磁相变温度TN值也随之下降; Co对Fe的部分替代使其磁电阻效应受到抑制.基于对其电子结构的分析,其磁电阻效应的起源以及Co的元素替代效应也在文中进行了讨论.
关键词:
双钙钛矿结构
2FeMoO6')" href="#">Sr2FeMoO6
磁电阻 相似文献
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通过X射线粉末衍射数据,用Rietveld精修方法分析了Te部分替换LaMnO3中La后,其晶格参数及其结构对称性所发生的变化.结果表明:Te掺杂LaMnO3系列样品具有R3C的晶格结构对称性,其MnO6八面体晶格还产生了伸张畸变,畸变程度随Te掺杂量的增加而增大.此外根据Mn—O—Mn键角、eg电子能带的带宽、A位离子平均半径及A位离子尺寸失配度等的变化特点,推测Te掺杂LaMnO3样品除居里温度等相变物理量将随x增加而非线性变化外,还可能产生自旋玻璃态、相分离等宏观现象.
关键词:
庞磁电阻效应
La-Te-Mn-O
X射线衍射
Rietveld精修 相似文献
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对Eu1-xSrxMnO3 (x=0.4, 0.5, 0.6, 0.7) 体系的磁结构进行了系统的研究. 通过核磁共振实验, 磁化测量, 并结合电输运测量结果表明, Sr的掺入使得 EuMnO3反铁磁母相中出现铁磁相. 铁磁相和反铁磁相的竞争导致样品在低温下的自旋玻璃行为.分析认为, Eu0.4Sr0.6MnO3和Eu0.3Sr0.7MnO3的磁结构在低温下呈现更加复杂的特征, 主要源于铁磁团簇的形成以及无序相的存在. 相似文献
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The effect of lattice dimerization on the magnetoresistance (MR) in organic spin valves is investigated based on the Su-Schrieffer-Heeger (SSH) model and the Green's function method. By comparing with the results for a uniform chain, we find that the dimerization of the molecular chain modifies the monotonic dependence of the MR on the bias to an oscillatory one. A sign inversion of the MR is observed when the amplitude of the dimerization is adjusted. The results also show that at a low bias, the MR through a dimerized chain decreases with the increasing bias as well as the increasing chain length, which is consistent with the experimental reports. A further understanding can be achieved by analyzing the electronic states and the spin-dependent transmission spectrum with the parallel and antiparallel magnetization orientations of the two ferromagnetic electrodes. 相似文献
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The effects of electric and magnetic fields on the current spin polarization and magnetoresistance in a ferromagnetic/organic semiconductor/ferromagnetic(FM/OSC/FM) system 下载免费PDF全文
From experimental results of spin polarized injection and transport in organic semiconductors(OSCs),we theoretically study the current spin polarization and magnetoresistance under an electric and a magnetic field in a ferromagnetic/organic semiconductor/ferromagnetic(FM/OSC/FM) sandwich structure according to the spin drift-diffusion theory and Ohm’s law.From the calculations,it is found that the interfacial current spin polarization is enhanced by several orders of magnitude through tuning the magnetic and electric fields by taking into account the specific characteristics of OSC.Furthermore,the effects of the electric and magnetic fields on the magnetoresistance are also discussed in the sandwich structure. 相似文献
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采用磁控溅射法制备的La1-xSrxMnO3 (LSMO)/TiO2异质pn结表现出很好的整流特性.室温电流电压特性曲线显示随着Sr掺杂的增加,扩散电压增大,这可能由于Sr掺杂的增加导致载流子浓度增大所致.电流电压变温特性曲线显示随着测量温度的降低,扩散电压增大,这可能由于随着测量温度的变化导致界面电子结构的变化所致.值得提出的,异质pn结电阻随温度变化曲线表现出单层LSMO的金属绝缘相变特性,并且在低测量温度时表现出随着测量温度的降低结电阻增大,这可能是由于宽带隙的TiO2的引入导致.
关键词:
异质结
整流特性
庞磁阻 相似文献
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Markus Wohlgenannt 《固体物理学:研究快报》2012,6(6):229-242
We review recent work in the field of organic spintronics, focusing on our own contributions to this field. There are two principle magnetoresistance effects that occur in organic devices. (i) Organic magnetoresistance (OMAR), which occurs in nonmagnetic organic semiconductor devices. For example, in devices made from the prototypical small molecule Alq3 OMAR reaches values of 10% or more at room temperature. (ii) Organic spin‐valve effects that occur in devices that employ ferromagnetic electrodes for spin‐polarized current injection and detection. We undertake an analysis of these two types of magnetoresistance with the goal of identifying the dominant spin‐scattering mechanism. Analysis of OMAR reveals that hyperfine coupling is the dominant spin‐coupling mechanism. Spin–orbit coupling, on the other hand, is important only in organic semiconductor materials containing heavy atoms. We explore the reasons why spin–orbit coupling is relatively unimportant in hydrocarbon materials. Next, we present a theory for spin diffusion in disordered organic semiconductors based on hyperfine coupling, taking into account a combination of incoherent carrier hopping and coherent spin precession in the random hyperfine magnetic fields. We compare our findings with experimental values for the spin‐diffusion length. Finally, we demonstrate a criterion that allows the determination whether the organic spin‐valves operate in the tunneling or injection regimes. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Anomalous anisotropic magnetoresistance in single-crystalline Co/SrTiO3(001) heterostructures 下载免费PDF全文
Shuang-Long Yang 《中国物理 B》2021,30(12):127302-127302
The anisotropic magnetoresistances (AMRs) in single crystalline Co(6 nm)/SrTiO3(001) heterostructures from 5 K to 300 K with the current direction setting along either Co[100] or Co[110] are investigated in this work. The anomalous (normal) AMR is observed below (above) 100 K. With the current along Co[100] direction, the AMR shows negative longitudinal and positive transverse magnetoresistances at T< 100 K, while the AMR is inverse with the current along Co[110]. Meanwhile, the amplitude ratio between Co[110] and Co[100] is observed to be as large as 29 at 100 K. A crystal symmetry-adapted model of AMR demonstrates that interplay between the non-crystalline component and crossed AMR component results in the anomalous AMR. Our results may reveal more intriguing magneto-transport behaviors of film on SrTiO3 or other perovskite oxides. 相似文献
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The effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors 下载免费PDF全文
We investigated the effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors.A Lorentz-type magnetoresistance is obtained from spin-orbit coupling-dependent spin precession under the condition of a space-charge-limited current.The magnetoresistance depends on the initial spin orientation of the electron with respect to the hole in electron-hole pairs,and the increasing spin-orbit coupling slows down the change in magnetoresistance with magnetic field.The field dependence,the sign and the saturation value of the magnetoresistance are composite effects of recombination and dissociation rate constants of singlet and triplet electron-hole pairs.The simulated magnetoresistance shows good consistency with the experimental results. 相似文献
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文章作者制备了以多种π-共轭有机半导体(orgnanic semincondutor, 简称OSEC)为中间层,La2/3Sr1/3MnO3(LSMO)和另一铁磁或非磁性金属为电极的有机二极管,测量了器件的磁致电阻和磁电致发光效应.器件显示了与LSMO电极类似的负磁电阻效应,但是它的电阻变化比LSMO电极本身的变化大3个数量级,而且器件还有正的磁电致发光效应.文章作者认为,这些磁场效应源于磁场作用下LSMO费米能级的异常移动,导致载流子在LSMO-OSEC界面注入的增强. 相似文献