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.

这项研究的目的是检查在铁磁金属/GAAS接口处圆形极化光激发的自旋极化电子的自旋滤波效应。这些样品用右或左圆极化的光照明，从样品正常方向通过磁层的波长为800-850 nm，从而在与膜平面的正常的磁场中检测到依赖性光电流。螺旋性依赖性光电流显示出清晰的场依赖性，对应于磁层的磁化过程。还在足以使磁化饱和的磁场中测量了螺旋依赖性光电流的偏置依赖性。磁圆二色性是Fe/GaAS样品反向偏置的主要主导，而在正向偏置处观察到了重要特征。我们将这种特征特征归因于依赖螺旋性光电流的偏置依赖性，即在Fe/GaAs界面处的自旋滤波效应。但是，自旋过滤的效率仅限于几％的值。同样，效率的任何显着增强都不会通过在界面插入MGO隧道障碍来获得任何显着的增强，这可能是由于MG0层的粗糙度和销孔的存在。对于FE_3O_4/GAAS样本，我们观察到在零BIA处依赖性光电的偏置依赖性中的相似特征。从这些组合结果，我们得出结论，尽管效率很小，但磁性金属层可以充当自旋滤波器，并用作自旋检测器。原子较平坦的层对于提高自旋检测效率是必要的。