Characteristics of the Al2O3 barrier with CoFeB pinned layer in magnetic tunnel junctions

Abstract

The magnetoresistance (MR) ratio of magnetic tunnel junctions (MTJs) depends on the structure and characteristics of the interface between ferromagnetic electrode and insulating layer. In order to understand the role of an amorphous layer as an electrode, the amorphous CoFeB and the crystalline CoFe were used for the pinned layers in MTJs and their properties were compared. When the CoFeB was used for the pinned layer, the MR ratio was higher than that of the CoFe pinned layer after annealing process. The reason for the higher MR of the CoFeB pinned layers are considered due to the chemically sharp interface formation. The chemically sharp interface means that B from the pinned layer gathers excess oxygen and Mn diffusion from the antifferomagnetic layer during the annealing is reduced by the amorphous CoFeB layer.