Spin-dependent transmission of highly polarized electrons through ferromagnet/semiconductor interfaces

将自旋极化电子束从砷化镓光电阴极发射到沉积在砷化镓光电阴极上的薄铁磁层中，并研究了通过铁磁/半导体界面的自旋依赖性。用极性相反的圆偏振光子辐照，可以激发具有相反自旋极化的极化电子。铁磁薄膜是一层3nm厚的GdTbFe，在薄膜与光电阴极之间插入一层2nm的氧化层，导致电子隧穿传输。沉积后，薄膜沿垂直于表面的方向磁化。在室温下测量了具有相反自旋极化的光电流。对于与铁磁薄膜极化相同的电子，电流增强，而相反极化的电子，电流减小。在本实验中，使用p-GaAs衬底作为光电阴极，因此估计光电子的极化约为30 ~ 35%。如果使用具有GaAs/GaAsP应变超晶格的光电阴极，则预期具有更清晰的依赖性，因为极化率预计超过85%。

A spin polarized electron beam emitted from a GaAs photocathode was injected into a thin ferromagnetic layer deposited on the GaAs photocathode and the spin-dependence of the transmission through the ferromagnet/semiconductor interface was investigated. Polarized electrons with opposite spin-polarizations were excited by irradiating with circularly polarized photons of opposite polarity. The ferromagnetic film was a 3nm thick layer of GdTbFe, and a thin oxide layer (2nm) was inserted between the film and the photocathode, which resulted in tunneling transmission of the electrons. After deposition, the film was magnetized in the direction perpendicular to the surface. Photo-currents with opposite spin polarizations were measured at room temperature. For electrons with the same polarization as that of the ferromagnetic films, the current was enhanced, while, on the other hand, the current was reduced in the case of the opposite polarization. In the present experiment, a p-GaAs substrate was used as the photocathode, and therefore the polarization of the photoelectrons was estimated as approximately 30〜35%. If a photocathode with a GaAs/GaAsP strained superlattice is used, a much clearer dependence is anticipated because polarization of more than 85% is expected.