Giant tunneling magnetoresistance and spin polarization in tunnel junctions and spin injectors

Superconducting tunneling spectroscopy (STS) was used in this study to determine the spin polarization in tunnel junctions and spin injectors. STS showed that the polarization of the tunneling current from the 3d transition metal ferromagnets (FM) through amorphous aluminum oxide tunnel barriers is about 40 to 50% and is largely independent of the FM crystal structure and orientation. However, the same 3d transition metal ferromagnets and their alloys, when formed in the bcc crystal structure, and in conjunction with crystalline magnesium oxide tunnel barriers exhibit much higher tunneling spin polarization values of up to ∼85%. Also, MgO based tunnel spin injectors for semiconductor spintronics was discussed.