Epitaxial τ phase MnAI thin films on MgO (001) with thickness-dependent magnetic anisotropy

摘要

In this study, ferromagnetic MnAI films were prepared by alternating Al/Mn quasi-monolayer deposition using a novel biased target ion beam deposition (BTIBD) technique. XRD results showed that the magnetic t phase was well formed in MnAI thin films (~10 nm), which grew epitaxially on single crystal MgO (001) substrates. The optimized saturation magnetization was ～394 emu/cc. Furthermore, we observed a thickness-dependent uniaxial anisotropy in ferromagnetic MnAI films, which was attributed to the change of the tetragonal lattice distortion as a function of film thickness. The relationship between the film thicknesses and saturation magnetizations suggested the existence of a magnetically dead layer ～2.7 nm with an extrapolated saturation moment around 523 emu/cc (～1.90 μ_B/Mn). This value has exceeded the experimental value in bulk materials and is close to the theoretically predicted magnetization (～1.975 μ_B/Mn).