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Current in heterogeneous tunnel junctions is studied in the framework of the parabolic conduction-band model. The developed model of the electron tunneling takes explicitly into account the difference of effective masses between ferromagnetic and insulating layers and between conduction subbands. Calculations for Fe/MgO/Fe-like structures have shown the essential impact of effective mass differences in regions (constituents) of the structure on the tunnel magnetoresistance of the junction. 相似文献
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采用溶胶凝胶法以及静电纺丝法, 利用热处理工艺, 成功制备出了多晶锐钛矿型TiO2纳米线, 通过两线法在室温下测试单根TiO2纳米线的V-I曲线来研究其电输运性能及磁阻效应. 结果表明: 在无光照环境下其V-I曲线为不过零点的直线, 零场电阻较大, 在磁场作用下电阻下降, 表现出负磁阻效应; 紫外光辐照环境下TiO2纳米线载流子浓度增加使得电阻变小, 然而在磁场作用下电阻增大, 表现为正磁阻效应. 紫外光辐照导致的载流子浓度变化, 使得负磁阻转变为正磁阻, 我们将磁阻变化归结为d电子局域导致的负磁阻与能带劈裂导致的正磁阻两种机理相互竞争的结果. 相似文献
14.
Low‐field magnetoresistance is an effective and energy‐saving way to use half‐metallic materials in magnetic reading heads and magnetic random access memory. Common spin‐polarized materials with low field magnetoresistance effect are perovskite‐type manganese, cobalt, and molybdenum oxides. In this study, we report a new type of spinel cobaltite materials, self‐assembled nanocrystalline NiCo2O4, which shows large low field magnetoresistance as large as –19.1% at 0.5 T and –50% at 9 T (2 K). The large low field magnetoresistance is attributed to the fast magnetization rotation of the core nanocrystals. The surface spin‐glass is responsible for the observed weak saturation of magnetoresistance under high fields. Our calculation demonstrates that the half‐metallicity of NiCo2O4 comes from the hopping eg electrons within the tetrahedral Co‐atoms and the octahedral Ni‐atoms. The discovery of large low‐field magnetoresistance in simple spinel oxide NiCo2O4, a non‐perovskite oxide, leads to an extended family of low‐field magnetoresistance materials. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
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《Physics letters. A》2020,384(32):126826
In this paper, hydrogenation is used for the generation of band gap in silicene and the hydrogenated silicene is then studied for its spintronic application. Upon hydrogenation, silicene transforms into a wide band gap material with a band gap of 3.32 eV. Parameters like magneto-resistance and spin-filtering efficiency of magnetic tunnel junction (MTJ) with CrO2 as semi-metallic electrodes and hydrogenated silicene as scattering region are found to increase compared to pristine silicene as scattering region. The simulation results show that the magneto-resistance of hydrogenated silicene remains above 85% (higher than the pristine counterpart) for the entire bias range. In addition, the spin-filtering efficiency in hydrogenated silicene reaches a value as high as 96% whereas in case of pristine silicene it remains below 90% for the entire bias range. 相似文献
17.
采用溶胶-凝胶法制备了不同烧结温度的钙钛矿类锰氧化物La0.67Sr0.33MnO3样品。实验结果表明,在1573 K以上烧结的样品,晶粒出现异常长大,晶界效应明显。随着烧结温度的提高,磁化强度逐渐增大,但样品的居里温度基本不变。此外,在1173和1573 K温度下烧结的样品,均出现了低于居里温度的金属-半导体导电行为转变。在合适的烧结条件下,可以观察到隧道磁电阻(TMR)和超大磁电阻(CMR)2种磁电阻效应。实验表明,自旋电子的输运,不仅与样品平均粒径的大小和密度有关,而且与晶界的微观结构有密切关系。 相似文献
18.
Hydrogen Treatment for Superparamagnetic VO2 Nanowires with Large Room‐Temperature Magnetoresistance
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Zejun Li Yuqiao Guo Prof. Zhenpeng Hu Jihu Su Jiyin Zhao Junchi Wu Jiajing Wu Yingcheng Zhao Prof. Changzheng Wu Prof. Yi Xie 《Angewandte Chemie (International ed. in English)》2016,55(28):8018-8022
One‐dimensional (1D) transition metal oxide (TMO) nanostructures are actively pursued in spintronic devices owing to their nontrivial d electron magnetism and confined electron transport pathways. However, for TMOs, the realization of 1D structures with long‐range magnetic order to achieve a sensitive magnetoelectric response near room temperature has been a longstanding challenge. Herein, we exploit a chemical hydric effect to regulate the spin structure of 1D V–V atomic chains in monoclinic VO2 nanowires. Hydrogen treatment introduced V3+ (3d2) ions into the 1D zigzag V–V chains, triggering the formation of ferromagnetically coupled V3+–V4+ dimers to produce 1D superparamagnetic chains and achieve large room‐temperature negative magnetoresistance (?23.9 %, 300 K, 0.5 T). This approach offers new opportunities to regulate the spin structure of 1D nanostructures to control the intrinsic magnetoelectric properties of spintronic materials. 相似文献
19.
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
20.
T. Yang 《Journal of magnetism and magnetic materials》2010,322(19):L53
MgO barrier degradation is studied in a tunneling magnetoresistance head with low resistance-area product. As the stress current is increased, the resistance is significantly reduced before the barrier breakdown, while the magnetoresistance ratio remains almost unvaried. At the same time, the bias dependence of the resistance becomes less affected by the bias polarity, suggesting that slight degradation occurs at the interface between MgO and the ferromagnetic electrode. Just before the breakdown, the bias dependence shows an increasing tendency, indicating the defect accumulation inside the MgO barrier. The results are helpful for understanding the mechanisms of barrier degradation, which is critical for developing future magnetic tunneling junction devices. 相似文献