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

Fully epitaxial magnetic tunnel junctions (MTJs) of Co
₂
Cr
_0.6
Fe
_0.4
Al (CCFA)/MgO/CCFA with exchange biasing were fabricated. The fabricated MTJs showed clear exchange-biased tunnel magnetoresistance (TMR) characteristics due to the CCFA/Ru/Co
₉₀
Fe
₁₀
/IrMn exchange-biased synthetic ferrimagnetic layer. The TMR characteristics were investigated as a function of in situ annealing temperature (T
_a
) for the upper CCFA layer. We obtained TMR ratios of 60% at room temperature (RT) and 238% at 4.2 K for MTJs with T
_a
of 400 degC, while those for MTJs with T
_a
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