Effect of localized antiferromagnetic phases at interfaces between AlO_x insulating barriers and Co_(50)Fe_(50) electrodes in magnetic tunnel junctions

摘要

Localized antiferromagnetic (LAFM) phases at interfaces between AlO_x insulating barriers and CoFe bottom electrodes were investigated. The LAFM phases were induced by interdiffusion of oxygen atoms into the bottom electrode during oxidation process. Observation in x-ray photoelectron spectroscopy exhibits the significant LAFM phases of CoO and FeO at 783 eV and 711 eV, respectively. The LAFM couplings sensitively . relevant to oxidation time are directly related to the coercivity field difference in a magnetoresistance (MR) curve. They also enhance the coercivity of a CoFe bottom electrode from 25 Oe up to 71.5 Oe, depending on oxidation time. These results explain well the better MR curves by a locally overoxidized state inside a CoFe bottom electrode.