L 1₀-FeAu Perpendicular Magnetic Tunnel Junction: A DFT + NEGF Study

This work examines the spin dynamic and transport properties of transition metal intermetallic alloy, L<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1_{0}$ </tex-math></inline-formula>-FeAu, using density functional theory (DFT) combined with the nonequilibrium Green’s function (NEGF) technique. The motivation behind this work is driven by the potential application of this ferromagnet in spintronic devices, where it can act as a magnetic electrode material for MgO-based perpendicular magnetic tunnel junction (p-MTJ) for spin transfer torque magnetic random access memories (STT-MRAMs). Our analyses show several advantages of L<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1_{0}$ </tex-math></inline-formula>-FeAu, like large bulk magnetic anisotropy energy (1.20 meV/f.u.), which contributes to higher thermal stability, relatively low Gilbert damping (0.0035), that helps to reduce the switching current, and also has spin-polarized <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta _{1}$ </tex-math></inline-formula> bands on Fermi surface, which can effectively provide higher tunneling magnetoresistance (TMR) for better read operation. In our analysis, we find that the TMR of FeAu-based MTJs (having 0.9 nm-thick MgO barrier) is around 34000%, which is eight times higher than that of our calculated conventional Fe-based p-MTJ. It was also found that the resistance-area (RA) product of FeAu MTJ is one order higher than that of Fe-based MTJ, which helps in improving switching efficiency, although the switching voltage can also increase. Overall, the collective computations demonstrate the importance of L<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1_{0}$ </tex-math></inline-formula>-FeAu ferromagnetic material for future STT-MRAMs.