Magnetoelectronics
Magnetoelectronics
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DOI：
10.1007/3-540-27164-3_2
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发表时间：
1998
期刊：
影响因子：
56.9
通讯作者：
Prinz
中科院分区：
文献类型：
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作者：
Prinz
2.1背景在巨磁电阻效应[2.1]的关键发现之前，磁性材料中的电输运研究仅限于一个非常小的研究群体。现在，十多年后，它已成为凝聚态物理和材料科学的主导主题之一，涉及全球数千名科学家。这是由于自旋极化输运的主题是一个有趣且具有挑战性的研究领域这一事实，以及可能存在于电子设备中的技术机会，这些电子设备具有基于载体自旋的新功能。最初的工作，围绕巨磁电阻（GMR）效应，处理分层材料都是金属。这引起了电子能带结构界的极大关注，因为在结构匹配（例如bcc Fe/Cr或fcc Co/Cu多层膜）的系统中观察到最大的影响，并且在界面处优先显示出一种自旋态的电子能带匹配[2.2]。这在图2.1中作了示意性的说明。下一个重要的突破是通过绝缘势垒观察到从一种磁性金属到另一种磁性金属的自旋极化隧穿[2.3]。这吸引了更多的研究人员，其中许多人以前曾在超导和约瑟夫森结领域工作过。现在的焦点已经从金属的体电子态转移到负责隧穿势垒的界面态。最近，焦点再次转移到包括自旋极化电流从铁磁体注入半导体[2.4]。这个焦点再次改变了电子状态的问题，涉及到运输，因为在半导体中，人们通常关注的是低k动量状态与低有效质量，而铁磁金属通常有高k和高有效质量。这种不匹配引起了人们对在这种分层材料中成功观察有用效果的可能性的担忧。事实上，仅仅是电导率的不匹配
2.1 BackgroundBefore the critical discovery of the giant magnetoresistance effect [2.1], the study of electrical transport in magnetic materials was confined to a very small community of researchers. Now, slightly more than a decade later, it has become one of the dominant themes of condensed matter physics and materials science involving thousands of scientists, worldwide. This is driven both by the fact that the subject of spin-polarized transport is an interesting and challenging field of study, and also by the technological opportunities which may lie in electronic devices, which have a new degree of functionality based upon the spin of the carrier. The initial work, centered around the giant magnetoresistance (GMR) effect, dealt with layered materials which were all metallic. This attracted considerable attention from the electronic band structure community, since the largest effects were seen in those systems which were both structurally matched (eg bcc Fe/Cr or fcc Co/Cu multilayers) and exhibited electronic band matching preferentially for one spin state at the interfaces [2.2]. This is illustrated schematically in Fig. 2.1. The next important breakthrough came with the observation of spin-polarized tunneling from one magnetic metal to another, through an insulating barrier [2.3]. This attracted an additional community of researchers, many of whom had previously worked in the field of superconductivity and Josephson junctions. The focus now shifted from the bulk electronic states of the metal, to the interface states responsible for tunneling through the barrier.Most recently, the focus has shifted again now to include the injection of spin polarized current from a ferromagnet into a semiconductor [2.4]. This focus again changes the issues of the electronic states involved in the transport, since in semiconductors one is generally concerned with low k momentum states with low effective mass, while ferromagnetic metals generally have high k and high effective mass. This mismatch has raised concerns about the likelihood of success in observing useful effects in such layered materials. Indeed, the mismatch in conductivity alone