Spin-valve magnetoresistance in Co/Si/（Co/Cu/Co） multilayers

A series of Co/Si/（Co/Cu/Co） multilayers and Co/Si/Co sandwiches were prepared by high vacuum electron-beam evaporation. It was found that a Si spacer （≥0.9 nm） could greatly decrease the interlayer coupling in Co/Si/Co sandwiches and there was no magnetoresistance（MR） or spin-valve MR in them due to the high resistivity of Si spacer. While in Co/Si/（Co/Cu/Co） multilayers, we observed a spin-valve MR of about 0.5% through a nominal 2.7 nm Si spacer at room temperature. The spin-valve MR in Co/Si/（Co/Cu/Co） multilayers was attributed to the enhanced spin polarization of conduction electrons caused by the top Co/Cu/Co sandwich with GMR mechanism and high spin-dependent scattering at Co/Cu interface.     

Microwave magnetoresistance in Ge:Mn nanowires and nanofilms

Abstract

The Lorentzian and spin-scattering components of magnetoresistance were found and distinguished in Ge:Mn thin films. The suppression of microwave magnetoresistance by the limitation of the dimensionality of Ge nanowires doped with Mn has been revealed. Spin-wave resonance in the long-ordered magnetic state and ferromagnetic resonance in GeMn clusters have been detected.     

Effects of Current-Injection on Superconductivity of YBa2Cu3O7-δ in La0.8Te0.2 MnO3/YBa2Cu3O7-δBilayer

La0.8Te0.2MnO3/YBa2Cu3O7-δ(F/S)bilayers were fabricated by electrophoretic technique. The thickness of La0.8Te0.2MnO3 is ～70 μm, the dimensions of YBa2Cu3O7-δ superconductor are 5 mm×10 mm×0.5 mm. The image of cross-sectional profile was measured by scanning electron microscopy (SEM). Standard four-probe method was used for YBa2Cu3O7-δ superconducting resistance measurements. Either 1 mA current is injected from S layer to F layer ( Iinj) or from F layer to S layer (-Iinj),the normal resistance is lower than that without current injection. The critical transition temperature is higher than that without current injection.     

中国大陆纬向石油富集带地质特征

从中国板块构造、盆地成因、产层主要时代等因素分析,中国大陆含油盆地可分为经向的伊兰一伊通一渤海湾一江汉等盆地带和纬向的准噶尔一二连一松辽等盆地带,两带共拥有中国石油产量和储量的绝对优势,因而分别被称为经向和纬向石油富集“黄金带”.在分析了渤海湾盆地与松辽盆地分属于经向和纬向石油富集带后,着重讨论了纬向石油富集带的特征,并与国内两类三种含油气构造单元对比,认为西北地区处于中国大陆今后石油发展战略重要位置,并有可能在准噶尔盆地腹地找到特大型油气田.     

不同制备工艺对多晶双钙钛矿Sr2FeMoO6室温磁电阻效应的影响

研究了固相反应法和溶胶-凝胶自燃法制备多晶Sr2FeMoO6块体样品的室温磁电阻效应,发现溶胶-凝胶自燃法制备的样品与固相反应法相比,室温磁电阻效应由2.9%上升到13.8%,增幅达3.76倍。溶胶-凝胶自燃法制备的前驱粉末为超微粉体,在烧结时能形成优异的晶界质量,需要的烧结温度低,结晶粒度小,晶界数目增多,使磁电阻增强;低的烧结温度易生成SrMoO4,加强绝缘势垒,因此具有好的磁电阻效应。     

Negative giant surface potential of vacuum-evaporated tris(7-propyl-8-hydroxyquinolinolato) aluminum(III) [Al(7-Prq)3] film

Negative giant surface potential was realized in a vacuum-evaporated film of tris(7-propyl-8-hydroxyquinolinolato) aluminum(III) [Al(7-Prq)₃]. Electroabsorption response of the film presented an inverted polarity to that of tris(8-hydroxyquinolinolato) aluminum (Alq₃), suggesting opposite noncentrosymmetry of molecular orientation. Asymmetric dice model with molecular geometric effect has been proposed, and propyl substitution at 7 position of the ligands was indicated to affects the molecular posture on the surface to invert the polarity of noncentrosymmetry. Our results opened a new possibility of controlling molecular orientation in a film for device applications.     

中国石油物探五十年──谨以此文祝贺中国地球物理学会成立五十周年

经过五十年的艰苦历程，中国石油物探形成了一支具有相当技术水平、丰富工作经验和庞大工业技术体系的队伍，她已成为中国油气勘查工作中相对独立的、十分重要的技术手段和提供信息量最大的资料来源，并被认为必须把她放到“先行之先”“重中之重”的地位。五十年来中国石油物探可分为三个发展时期，不同时期有不同的发展特点，今天她已走上基本成熟的阶段，并已跻身于世界石油物探队伍的先进行列。但要使石油物探适应２１世纪中国石     

金属颗粒膜巨磁电阻效应的理论研究

由于巨磁阻效应材料在磁记录设备和传感器的潜在应用,具有该效应的材料得到了广泛地研究。特别是继金属多层膜之后的金属磁性颗粒膜,由于其制备简单,巨磁阻效应的机理较为复杂,受到人们的青睐。综述了金属磁性颗粒膜中巨磁阻效应的理论。在此基础上,指出了当前值得注意的研究方向。     

Electric Field Induced Suppression of the Magnetoresistance of Dilute Magnetic Semiconductor Trilayers

In semiconductor spintronic devices, the semiconductor is usually lightly doped and nondegenerate, and moderate electric fields can dominate the carrier motion. We recently derived a drift-diffusion equation for spin polarization in the semiconductors by consistently taking into account electric-field effects and nondegenerate electron statistics and identified a high-field diffusive regime that has no analog in metals. Here high fields are argued to substantially reduce the magnetoresistance observable in a recent experiment on magnetic-semiconductor–nonmagnetic-semiconductor–magnetic-semiconductor trilayers.     

磁控溅射法制备IrMn顶钉扎自旋阀研究

通过高真空直流磁控溅射的方法,在玻璃和硅上淀积了结构为Ta/NiFe/CoFe/Cu/CoFe/IrMn/Ta的IrMn顶钉扎自旋阀薄膜。通过结构的改善和工艺条件的优化,自旋阀的磁电阻率达到9.12％,矫顽力为1.04×(10~3/4π)A/m。研究了Ta缓冲层厚度(小于6nm)对晶格结构和自旋阀性能的影响。结果表明,Ta为3nm时自旋阀磁电阻率最大,而矫顽力随着Ta厚度增大而减小。利用CoFe/Cu/CoFe SAF结构替换掉与IrMn相邻的CoFe被钉扎层,使交换偏置场从原来没有SAF的180×(10~3/4π)A/m上升到600×(10~3/4π)A/m左右,且交换偏置场随着SAF结构中两层CoFe的厚度差减小而增大。研究了RIE对自旋阀性能的影响,发现2min的RIE能使矫顽力减小33％,而磁电阻率几乎不受影响。