FERROMAGNETIC DOUBLE QUANTUM WELL TUNNEL MAGNETORESISTANCE DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a ferromagnetic double quantum well tunnel magnetoresistance device which obtains an infinite tunnel magnetoresistance ratio by a desired bias voltage, utilizing a two-dimensional electron (hole) system. SOLUTION: This device has a heterostructure composed of a first nonmagnetic barrier layer 2, a first ferromagnetic quantum well layer 4, a second nonmagnetic barrier layer 6, a second ferromagnetic quantum well layer 8, a third nonmagnetic barrier layer 10 laminated one above another. The first ferromagnetic quantum well layer 4 and the second ferromagnetic quantum well layer 8 are each a sufficiently thin layer, compared to the de Broglie's wavelength of carriers serving conduction, the first ferromagnetic quantum well layer 4 and the second ferromagnetic quantum well layer 8 are formed, so that the carriers become two-dimensional electrons (holes) upon confining them in quantum wells, the first nonmagnetic barrier layer 2, the second nonmagnetic barrier layer 6 and the third nonmagnetic barrier layer 10 are about several nanometers thin sufficient for the carriers to tunnel. Tunneling tends to occur, when two quantum wells are magnetized in the same direction, but the tunneling is inhibited when magnetization is antiparallel.