Tunable magnetic anisotropy in Cr-trihalide Janus monolayers.

Achieving a two-dimensional material with tunable magnetic anisotropy is highly desirable, especially if it is complemented with out-of-plane electric polarization, as this could provide a versatile platform for spintronic and multifunctional devices. Using first principles calculations, we demonstrate that the magnetic anisotropy of Cr-trihalides become highly sensitive to mechanical strain upon structural inversion symmetry breaking through the realization of Janus monolayers. This remarkable feature, absent in pristine Cr-trihalide monolayers, enables mechanical control of the direction of the easy axis: biaxial compressive/tensile strain supports in-plane/out-of-plane orientation of the easy axis. The magnetic exchange itself shows higher sensitivity to compressive than to tensile strain, while in general the Janus monolayers maintain ferromagnetic ordering in the studied range of strain.