We propose a ferromagnetic Heusler alloy that can switch between a metal and a half-metal. This effect can provide tunable spintronics properties. Using the density functional theory with reliable implementations of the electron correlation effects, we find ${\mathrm{Mn}}_2\mathrm{ScSi}$ total energy curves consisting of distinct branches with a very small energy difference. The phase at low lattice crystal volume is a low magnetic half-metallic state while the phase at high lattice crystal volume is a high magnetic metallic state. We suggest that the transition between half-metallic and metallic states can be triggered by a triaxial contraction/expansion of the crystal lattice or by an external magnetic field if we assume that the lattice is cubic and remains cubic under expansion/contraction. However, the phase at high volume can also undergo an austenite-martensite phase transition because of the presence of Jahn-Teller active $3d$ electrons on the Mn atoms.

• Received 13 November 2020
• Revised 29 December 2020
• Accepted 25 January 2021

DOI:https://doi.org/10.1103/PhysRevB.103.054414