Tunnel magnetoresistance in fully epitaxial MgO double barrier magnetic tunnel junctions

The TMR properties of epitaxial Fe(100)/MgO(100)/Fe(100)/MgO(100)/Fe(100) double barrier magnetic tunnel junctions (DMTJs) is reported. Both TMR and I-V characteristics were measured at room temperature using a dc four probe method. Single barrier MTJs (SMTJs) were used as references. A pseudo-spin-valve type TMR curve originated from the different magnetic switching fields (H_sw) for the both top and bottom Fe layers (H_sw = 48 Oe) and for the middle Fe layer (H^sw = 14 Oe). Higher TMR ratios of up to 110% (average: 89%) compared with the SMTJ (average: 77%) are observed for the DMTJ although the magnitude of the TMR ratio for the DMTJ has been reported to be smaller than that for the SMTJs.