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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.

本研究的目的是检查铁磁金属/GaAs 界面上圆偏振光照射下 GaAs 中激发的自旋极化电子的自旋过滤效应。使用磁控溅射和反应 MBE 技术生长了几种类型的样品，例如 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穿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到螺旋性依赖的光电流。螺旋度相关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。还在足以使磁化饱和的磁场中测量了螺旋度相关光电流的偏置依赖性。 Fe/GaAs 样品的反向偏压下磁圆二色性占主导地位，而在正向偏压下则观察到了显着特征。我们将螺旋度相关光电流的偏压依赖性归因于 Fe/GaAs 界面处的自旋过滤效应。然而，旋转过滤的效率被限制在百分之几的值。此外，通过在界面处插入 MgO 隧道势垒并不能显着提高效率，这可能是由于 MgO 层的粗糙度和针孔的存在。对于Fe_3O_4/GaAs样品，我们在零偏压下观察到螺旋性相关光电流的偏压依赖性的类似特征。从这些综合结果中，我们得出结论，磁性金属层可以充当自旋过滤器并充当自旋探测器，尽管效率很小。原子平坦层对于提高自旋检测效率是必要的。