Abstract
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. Although anomalous Hall effects may contribute to spin-current generation, the OHE plays a principal role in the generation of spin current when electrons and holes have approximately the same transport characteristics. 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 measurement of yttrium dihydride and preliminary results of the magnetization measurement of hydrogenated films of gadolinium.