Generation of Spin Current in Bipolar Conductors with Quasi-Zero Hall Coefficients

研究了由外加磁场引起的普通霍尔效应（OHE）作为自旋电流产生的机制。已经从理论上阐明，在开路条件下，当自旋极化的电子和空穴同时作为移动的载流子存在时，OHE可以有助于自旋电流的产生。这种OHE对自旋电流产生的贡献是由横向速度具有相同方向的电子和空穴的稳态运动学引起的。本文根据准零霍尔系数（QZHC）导体YH_2和Gd_xY_ H_2的磁输运测量结果，讨论了类质同象电子和空穴系统可能材料的实验问题<1-x>。为了验证自旋电流的产生，我们用两种类型的霍尔器件研究了自旋注入对这些QZHC导体的影响，其中电流沟道区是（A）磁性材料Gd_xY_<1-x>H_2（x ≤ 0.4）和（B）Gd_xY_H_2，但具有Co源极，短沟道长度约为10 μm。在霍尔器件A和B中均观察到了巨大的反常霍尔电阻率和正的横向磁电阻率，表明了自旋电流的产生。

The ordinary Hall effect (OHE), which is caused by an external magnetic field, was studied as a mechanism for the generation of spin current. It has been theoretically elucidated that, under an open-circuit condition, the OHE can contribute to spin-current generation when spin-polarized electrons and holes are simultaneously present as mobile carriers. This OHE contribution to spin current generation is caused by the steady-state kinematics of electrons and holes whose transverse velocities have the same direction. The experimental aspects of possible materials for the isomorphic electron and hole systems are argued on the basis of the experimental results of the magnetotransport measurements of the quasi-zero Hall coefficient (QZHC) conductors YH_2 and Gd_xY_<1-x>H_2. For experimental verification of spin current generation, we have investigated the influence of spin injection in these QZHC conductors by employing two type of Hall devices, the current channel region of which are (A) magneticmaterial Gd_xY_<1-x>H_2 (x≒0.4) and (B) nonmagnetic YH_2 but having Co source electrodes and a shortchannel length of approximately 10 μm. Huge anomalous Hall resistivity and positive transversemagnetoresistivity are observed in both Hall devices A and B, showing the generation of spin current.