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Spin injection into magnetic alloys using optical spin excitation technique

使用光学自旋激发技术自旋注入磁性合金

基本信息

批准号：
16360311
负责人：
YAMAZAKI Yohtaro
金额：
$ 9.86万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360311/
关键词：
Optical spin excitation Spin injection Magnetic metal Spin filtering

项目摘要

The purpose of this study is to examine the spin filtering effect of spin polarized electrons excited in GaAs with illumination of circularly polarized light at the ferromagnetic metal/GaAs interfaces.Several types of samples, e.g., Fe/GaAs, Fe/MgO/GaAs, Fe_3O_4/GaAs, were grown using magnetron sputtering and reactive MBE techniques. These samples were illuminated with right or left circularly polarized light with a wavelength of 800-850 nm from sample normal direction through the magnetic layer, thereby helicity dependent photocurrent was detected in a magnetic field normal to the film plane. The helicity dependent photocurrent showed clear field dependence, corresponding to the magnetization process of the magnetic layer. The bias dependence of the helicity dependent photocurrent was also measured in a magnetic field sufficient to saturate the magnetization. Magnetic circular dichroism was predominant for reverse bias for Fe/GaAs samples, while a significant feature was observed at a forward bias. We attribute this characteristic feature in the bias dependence of helicity dependent photocurrent to spin filtering effect at the Fe/GaAs interface. The efficiency of the spin filtering, however, is limited to a value to a few %. Also, any significant enhancement in the efficiency was not obtained by inserting an MgO tunneling barrier at the interface, presumably due to the roughness of the Mg0 layer and the presence of pin holes. For Fe_3O_4/GaAs samples, we observed a similar feature in the bias dependence of the helicity dependent photocurret at zero bias.From these combined results, we conclude that magnetic metal layer can act as a spin filter and work as a spin detector, although the efficiency is small. Atomically flat layers are necessary to improve the spin detection efficiency.

本研究的目的是研究GaAs中自旋极化电子在铁磁金属/GaAs界面上被圆偏振光激发时的自旋过滤效应。用磁控溅射和反应分子束外延技术生长了Fe/GaAs、Fe/MgO/GaAs、Fe_3O_4/GaAs。用波长为800-850 nm的右旋或左旋圆偏振光从样品法线方向通过磁性层照射这些样品，从而在垂直于膜平面的磁场中检测螺旋度依赖性光电流。螺旋度依赖的光电流表现出明显的场依赖性，对应于磁性层的磁化过程。的螺旋度依赖的光电流的偏置依赖性也被测量在一个磁场足以饱和的磁化。磁性圆二色性是占主导地位的Fe/GaAs样品的反向偏置，而一个显着的功能，观察到在正向偏置。我们属性的螺旋度依赖的光电流的偏置依赖于在Fe/GaAs界面的自旋过滤效应的特性。然而，自旋滤波的效率被限制在几个百分比的值。此外，通过在界面处插入MgO隧穿势垒而没有获得效率的任何显著增强，这可能是由于Mg 0层的粗糙度和针孔的存在。对于Fe_3O_4/GaAs样品，我们观察到了类似的零偏压下螺旋度相关的光电流随偏压的变化特征，从这些综合结果可以得出结论：磁性金属层既可以作为自旋过滤器，也可以作为自旋探测器，虽然效率很小。原子平坦层对于提高自旋检测效率是必要的。