Thickness and composition dependencies of magnetization and perpendicular magnetic anisotropy of Heusler-like alloys based [formula omitted] superlattices

Abstract

Finding materials that possess high perpendicular magnetic anisotropy (PMA) and low magnetization is a key challenge for the potential application to the magnetic tunnel junction (MTJ). Through systematic density functional theory (DFT) calculations, we have studied a series of MnxGa|Co2FeAl (x = 1, 1.66, 3) superlattice (SL) models by individually changing the thickness of MnxGa hard-magnetic layers and Co2FeAl soft-magnetic layers as well as controlling the interface magnetic couplings. Our results demonstrated that total magnetic moments of the SLs can be well balanced to a small (zero) value as the antiferromagnetically coupled MnxGa and Co2FeAl layers have the matching thickness and appropriate interface. Strong PMAs of MnxGa bulks can be well preserved in SLs, being up to 0.38, 0.37, 0.22 meV/Mn for x = 1, 1.66, 3, respectively, which are weakly dependent on the layered thickness (flexible lattice constants of SLs) but strongly on the magnetic coupling with Co2FeAl layers. The ferromagnetic/antiferromagnetic coupling at Mn-Co interface often generates small/large negative interface PMA and thus it would diminish the PMA of SLs; however, Ga-Co interface was found to give large/small positive contribution to the PMA of SLs. Typically, Ga-Co (MnGa-Co) interface is proposed to be the most favorable one for experimentally heteroepitaxial growth of MnxGa|Co2FeAl SLs, because it can guarantee these SLs to present high stability, large PMAs, and tunable magnetic moments.