First Principles Study of Atomic-Scale Al2O3 Films as Insulators for Magnetic Tunnel Junctions

Abstract
We performed density-functional calculations with Al/Al2O3/Al structures as models to study Al2O3 tunnel barriers for magnetic tunnel junctions. We found that aluminum oxide films thicker than 4.6 Å have pseudogaps without substantial gap states, which suggests that these films have good insulating properties. This finding is consistent with an experimental result where a large magnetoresistance ratio was attained with a film thickness of about 8 Å.