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1.
Epitaxial oxide trilayer junctions composed of magnetite (Fe3O4) and doped manganite (La0.7Sr0.3MnO3) exhibit inverse magnetoresistance as large as -25% in fields of 4 kOe. The inverse magnetoresistance confirms the theoretically predicted negative spin polarization of Fe3O4. Transport through the barrier can be understood in terms of hopping transport through localized states that preserve electron spin information. The junction magnetoresistance versus temperature curve exhibits a peak around 60 K that is explained in terms of the paramagnetic to ferrimagnetic transition of the CoCr2O4 barrier.  相似文献   

2.
介绍了一类增强磁电阻效应的新型稀土锰酸盐多晶颗粒复合体系及其化学制备方法,并对增强的机理进行了初步的探讨。  相似文献   

3.
4.
在5%Nb掺杂的SrTiO3衬底上用磁控溅射法外延生长了La1/aCa7/aMnO3薄膜形成异质结,该异质结有类似于传统P-n结的整流特性.磁场下扩散电压减小,当温度低于130 K以下,扩散电压的减小非常明显.这和在此温度以下,La1/8Ca7/aMnO3出现自旋倾斜态密切相关.我们计算出异质结的结电阻和磁致电阻(MR),在不同大小的正负偏压,不同磁场下,都得到负的MR值.我们给出界面附近的La1/8Ca7/8MnO3的能带结构并分析了外加磁场对洪德耦合,Jahn-Teller畸变等机制的作用,来解释该异质结的磁输运行为.结果有助于了解高Ca掺杂锰氧化物异质结的性质.  相似文献   

5.
Physics of the Solid State - The temperature dependence of the voltage induced by spin current is studied in the epitaxial thin-film La0.7Sr0.3MnO3/SrIrO3 heterostructure deposited on a...  相似文献   

6.
P Raychaudhuri  C Mitra  K Dorr  KH Muller  G Kobernik  R Pinto 《Pramana》2002,58(5-6):1179-1182
Hole-doped rare-earth manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 both show a metal-insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal-insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La0.7Ce0.3MnO3 could be a minority spin carrier ferromagnet. The implication of this observation is discussed.  相似文献   

7.
Physics of the Solid State - Crystalline samples of the (La1 – yEuy)0.7Pb0.3MnO3 (y = 0, 0.2, 0.4, 0.5, 0.6, and 0.8) manganite solid solutions have been grown. Temperature...  相似文献   

8.
Physics of the Solid State - Abstract—Temperature dependence of attenuation of magnetic spin precession in two-layer structures with a Pt top layer based on a La0.7Sr0.3MnO3 (LSMO) epitaxial...  相似文献   

9.
In this paper, the electronic transport of La(0.7)(Sr,Ca)(0.3)MnO(3) films grown by pulsed laser deposition on a LaAlO(3)(001) substrate with deep parallel structured steps and a 30° symmetric bicrystal SrTiO(3)(001) substrate have been discussed. The electronic transport properties have been related to the well-known extrinsic transport of bulk manganite compounds. The spin-glass-like behavior with a characteristic peak at 20 K and domain formation at the grain boundary is observed. Further, it has been quantified from the resonant tunneling model that mixed magnetic interactions play a significant role in the manganite films deposited on step edges.  相似文献   

10.
Electron spin-polarized tunneling is observed through an ultrathin layer of the molecular organic semiconductor tris(8-hydroxyquinolinato)aluminum (Alq3). Significant tunnel magnetoresistance (TMR) was measured in a Co/Al2O3/Alq3/NiFe magnetic tunnel junction at room temperature, which increased when cooled to low temperatures. Tunneling characteristics, such as the current-voltage behavior and temperature and bias dependence of the TMR, show the good quality of the organic tunnel barrier. Spin polarization (P) of the tunnel current through the Alq3 layer, directly measured using superconducting Al as the spin detector, shows that minimizing formation of an interfacial dipole layer between the metal electrode and organic barrier significantly improves spin transport.  相似文献   

11.
Taking into account the nonequilibrium spin accumulation, we apply a quantum-statistical approach to study the spin-polarized transport in a two-dimensional ferromagnet/semiconductor/ferromagnet (FM/SM/FM) double tunnel junction. It is found that the effective spin polarization is raised by increasing the barrier strength, resulting in an enhancement of the tunneling magnetoresistance (TMR). The nonequilibrium spin accumulation in SM may appear in both antiparallel and parallel alignments of magnetizations in two FMs, in particular for high bias voltages. The effects of spin accumulation and TMR on the bias voltage are discussed.  相似文献   

12.
Kida N  Takahashi K  Tonouchi M 《Optics letters》2004,29(21):2554-2556
Terahertz (THz) radiation from voltage-biased photoswitching devices made on magnetoresistive manganite Pr0.7Ca0.3MnO3 have been investigated for thin films grown under different conditions. We find that the temperature dependence of THz radiation near the charge-ordering temperature strongly depends on the growth condition of Pr0.7Ca0.3MnO3, whereas THz radiation shows no such temperature dependence near the spin-ordering temperature.  相似文献   

13.
We report spin transport through the silicon in novel magnetic junction with half metallic as free layer and metallic as pinned layer. We used La0.7Sr0.3MnO3 as free layer, FeCo as pinned layer and studied the magnetoresistance through silicon as spacer layer. We fabricated this magnetic tunnel junction using RF/DC sputtering technique over SrTiO3 substrate. Tunneling magnetoresistance (TMR) measurement for this junction at room temperature was found to be 1.1 %. At 2 K, we found a large magnetoresistance of 396 %. TMR found to be increased with decreasing temperature. The results are discussed.  相似文献   

14.
As proposed by Herminghaus, a hierarchical structure could render any surface nonwettable as long as the roughness amplitude at small scales is sufficient to suspend a free liquid surface. Recently we reported that the wettability of La0.7Sr0.3MnO3, an intrinsic hydrophilic oxide, can be tuned from superhydrophilicity to superhydrophobicity by hierarchical microstructures generated by annealing the coatings of La0.7Sr0.3MnO3 powder in nanometric scale at different temperatures. Here we further demonstrate the similar phenomenon observed on LaMaO3 coatings, which conforms THAT the surface geometrical structure is a key factor to determine the wettability.  相似文献   

15.
La0.7-xCexCa0.3MnO3低场磁电阻的晶格效应   总被引:1,自引:0,他引:1  
以稀土元素铈部分替换钙钛矿结构亚锰酸盐中的镧,使A位离子半径减小.由此在晶格中产生的内压将影响到B位d轨道与O位p轨道之间交叠形成的电子活性能带.本文以固相反应法制备了多晶La0.7-xCexCa0.3MnO3样品(x=0,0.05,0.10,0.20),测量并研究了电阻、低场磁电阻与温度(77K~300K)之关系.实验表明,随Ce替代量的增加,磁电阻(MR)峰值无显著变化,而MR峰值出现的温度Tp则递减.关于"减小可能导致Mn-O-Mn键角减小而最终使Tc降低"的见解可解释该实验结果.  相似文献   

16.
朱林  陈卫东  谢征微  李伯臧 《物理学报》2006,55(10):5499-5505
在NM/FI/FI/NM型双自旋过滤隧道结(此处NM为非磁金属层,FI为铁磁绝缘体或半导体层)的基础上,我们提出一种NM/FI/NI/FI/NM新型双自旋过滤隧道结(此处NI表示非磁绝缘体或半导体层). 插入NI层的目的是为了避免原双自旋过滤隧道结中相邻FI层界面处磁的耦合作用所导致的对隧穿磁电阻的不利影响. 在自由电子近似的基础上,利用转移矩阵方法,对NM/FI/NI/FI/NM新型双自旋过滤隧道结的隧穿电导、隧穿磁电阻与FI层及NI层厚度的变化关系以及随偏压的变化关系进行了理论研究.计算结果表明,在NM/FI/NI/FI/NM新型双自旋过滤隧道结中仍可以得到很大的TMR值. 关键词: 双自旋过滤隧道结 隧穿磁电阻 非磁绝缘(半导)体间隔层  相似文献   

17.
We present the structure of the fully relaxed (001) surface of the half-metallic manganite La0.7Sr0.3MnO3, calculated using density functional theory. Two relevant ferroelastic order parameters are identified and characterized. The known tilting of the oxygen octahedra, which is present in the bulk phase, decreases towards the surface. A ferrodistortive Mn off-centering, triggered by the surface and not reported before, decays monotonically into the bulk. This distortion affects neither the half-metallicity nor the zero-temperature magnetization, but does change the effective spin-spin interactions, and thus the temperature dependence of the magnetic properties.  相似文献   

18.
We experimentally studied the transport properties and magnetoresistance behavior of a La0.7Ce0.3MnO3/SrTiO3 (doped by 1 wt% Nb) junction. Based on the analyses of the current-voltage relations and the depletion width, we conclude that the dominant transport mechanism of the junction is tunneling. The magnetoresistance of the junction is negative throughout the whole bias voltage range (from −1 V to 0.4 V) and the whole temperature range (below 300 K). It is believed that the magnetic field depresses the junction resistance by reducing the depletion width of the junction.  相似文献   

19.
Current-induced switching from a metallic to an insulating state is observed in phase-separated states of (La(1-y)Pr(y))0.7Ca0.3MnO3 (y=0.7) and Nd(0.5)Ca(0.5)Mn(1-z)Cr(z)O3 (z=0.03) crystals. The application of magnetic fields to this current-induced insulating state causes a pronounced low-field negative magnetoresistance effect [rho(H)/rho(0)=10(-3) at H=1 kOe]. The application of a constant voltage also causes the breakdown of the Ohmic relation above a threshold voltage. At voltages higher than this threshold value, oscillations in currents are observed. This oscillation is well reproduced by a simple model of local switching of a percolative conduction path.  相似文献   

20.
The temperature and voltage dependence of spin transport is theoretically investigated in a new type of magnetic tunnel junction, which consists of two ferromagnetic outer electrodes separated by a ferromagnetic barrier and a nonmagnetic (NM) metallic spacer. The effect of spin fluctuation in magnetic barrier, which plays an important role at finite temperature, is included by taking the mean-field approximation. It is found that, the tunnel magnetoresistance (TMR) and the electron-spin polarization depend strongly on the temperature and the applied voltage. The TMR and spin polarization at different temperatures show an oscillatory behavior as a function of the NM spacer thickness. Also, the amplitude of these oscillations is regularly reduced when the temperature increases. The maximum TMR value, varies approximately from 270 in reverse bias (at T = 0 K) to 25 in forward bias (at ).Received: 25 June 2004, Published online: 14 December 2004PACS: 72.25.Hg Electrical injection of spin polarized carriers - 73.23.Ad Ballistic transport - 73.40.Gk Tunneling  相似文献   

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