Fabrication of Fully Epitaxial Co $_{2}$Cr$_{0.6}$ Fe$_{0.4}$Al/MgO/Co

摘要

Fully epitaxial magnetic tunnel junctions (MTJs) of Co2Cr0.6Fe0.4Al (CCFA)/MgO/CCFA with exchange biasing were fabricated. The fabricated MTJs showed clear exchange-biased tunnel magnetoresistance (TMR) characteristics due to the CCFA/Ru/Co90Fe10/IrMn exchange-biased synthetic ferrimagnetic layer. The TMR characteristics were investigated as a function of in situ annealing temperature (Ta) for the upper CCFA layer. We obtained TMR ratios of 60% at room temperature (RT) and 238% at 4.2 K for MTJs with Ta of 400 degC, while those for MTJs with Ta of RT (i.e., having an as-deposited upper CCFA layer) were 17% at RT and 80% at 4.2 K. These results clearly suggest that the spin polarization of the as-deposited upper CCFA layer was significantly increased by in situ annealing