New noncollinear antiferromagnet Mn3Al for antiferromagnetic spintronics

Abstract

Hexagonal noncollinear antiferromagnets, such as Mn₃Sn, Mn₃Ge, and Mn₃Ga, have garnered significant attention in recent years due to their potential for supplying large anisotropic anomalous and spin Hall conductance. In particular, noncollinear antiferromagnetic tunnel junctions have been fabricated, demonstrating their applications in antiferromagnetic spintronics in future. However, hexagonal Mn₃Al, a noncollinear antiferromagnet that has non-heavy metal elements, has never been reported. In this study, we not only predict the noncollinear antiferromagnet Mn₃Al through first-principles calculations and experimentally confirm the existence of hexagonal Mn₃Al, but also predict the existence of large anomalous Hall conductance for Mn₃Al. Our calculations reveal that Mn₃Al can be utilized in antiferromagnetic tunnel junctions and possesses anisotropic anomalous Hall conductance. Our calculations show a large ${\sigma }_{zx}$ = 1398 ${\mathrm{(\Omega \cdot cm)}}^{-1}$ above the Fermi level, which is caused by the Weyl points in momentum space for Mn₃Al. ${\sigma }_{zx}$ could be raised from 99.7 ${\mathrm{(\Omega \cdot cm)}}^{-1}$ for Mn₃Al to 412 ${\mathrm{(\Omega \cdot cm)}}^{-1}$ for Mn₃Al_0.5Si_0.5 at Fermi level by substituting the Al atoms with Si atoms. More Si content further raises the value of ${\sigma }_{zx}$ to a maximum 952 ${\mathrm{(\Omega \cdot cm)}}^{-1}$ for Mn₃Al_0.35Si_0.65 within the rigid band approximation. Furthermore, the films grown on Si(111) substrates suggest compatibility with semiconductor devices, thus broadening the applications of Mn₃Al and expanding the family of noncollinear antiferromagnets.