Patent ID: 7755929

Claim:
A spin injection device comprising a first tunnel junction and a second tunnel junction which have a common electrode composed of a nonmagnetic conductor and each of which has a counterelectrode composed of a ferromagnet, wherein: said first tunnel junction is a tunnel junction having an insulator interposed between said nonmagnetic conductor and said ferromagnet; said second tunnel junction is a tunnel junction in which an insulator, a ferromagnet, a nonmagnetic metal and said ferromagnet are successively layered on said nonmagnetic conductor, the ferromagnets at opposite sides of said nonmagnetic metal being magnetically coupled together antiparallel to each other via said nonmagnetic metal; said first and second tunnel junctions are disposed spaced apart from each other by a distance that is shorter than a spin diffusion length of said nonmagnetic conductor; said first tunnel junction is a tunnel junction for spin injection therein from a current (I) flowing from said ferromagnetic metal in the first tunnel junction into said nonmagnetic conductor when a positive voltage is applied to said common electrode and a negative voltage is applied to said ferromagnet in the first tunnel junction and said first tunnel junction is a tunnel junction to flow spin current (Is) between said first tunnel junction and said second tunnel junction, said second tunnel junction is a tunnel junction for detection between said ferromagnetic metal in said second tunnel junction and said nonmagnetic conductor therein of a voltage accompanying the spin injection of said first tunnel junction, and said nonmagnetic conductor is a semiconductor, or a semimetal having lower carrier density than a nonmagnetic metal wherein an output resistance defined by an equation below detected at said second tunnel junction of the spin injection device is at least 1.5Ω, Rs =( Vs )/ Is where Vs is a voltage difference of the detected voltage of said second tunnel junction with magnetization reversal of said ferromagnet of said first tunnel junction by an applied external magnetic field, and Is represents said spin current between said first tunnel junction and said second tunnel junction.