L10-ordered MnAl thin films with high perpendicular magnetic anisotropy using tin underlayers on Si substrates

Ferromagnetic L1₀-ordered τ-phase MnAl thin films have been shown to exhibit high perpendicular magnetic anisotropy (K_u > 10⁷ ergs/cm³), moderate saturation magnetization (M <; 600 emu/cm³), and low Gilbert damping parameter (α = 0.006). x-MnAl is also rare earth- and precious metal-free, making it an attractive candidate for a variety of applications such as magnetic recording, nonvolatile memory technologies, spintronic devices, permanent magnets, etc. However, achieving the necessary L1₀-ordering for perpendicular anisotropy in MnAl thin films has proven challenging and highly sensitive to deposition conditions and underlayers used. Using MgO underlayers, we previously demonstrated MnAl thin films with high perpendicular magnetic anisotropy (PMA) on Si substrates for the first time. However, MgO is an insulator, which presents two major challenges. First, MgO must be RF-sputtered, which results in low deposition rates, re-sputtering, and therefore the potential for MgO contamination in undesirable locations. Second, since it is an insulator, MgO impedes the use of MnAl film stacks as the bottom electrode in a magnetic tunnel junction (MTJ) for spintronic applications.