Designed metal-insulator transition in low-symmetry magnetic intermetallics

Compounds exhibiting half-metallic character and metal-insulator transitions draw considerable attention in condensed-matter and materials physics due to their potential use in spintronics. Here we show that specific electron doping plays a crucial role in tailoring thermodynamic, structural, electronic, and magnetic properties of materials derived from low-symmetry magnetic intermetallics, exemplified on triclinic Mn₄Al₁₁. Upon chemical doping of Al by Ge, we predict improved phase stability and adherence to a generalized “18-n rule” governing closed-shell configurations in intermetallic with narrow bandgaps. Validating experiments include measurements of phase stability and electronic transport properties of electron-doped Mn₄Al₁₀Ge that crystallizes in the Mn₄Al₁₁-type structure, confirming the bandgap opening as predicted by chemical analysis and density-functional theory. Here we also demonstrate theoretically that hydrostatic pressure enhances the predicted half-metallic gap in the up-spin channel, which leads to a ferrimagnetic-to-ferromagnetic transition driven by Mn-Mn charge ordering in the Mn₄Al₁₁ parent. We have also discussed the generality of our approach in predicting the design of other classes of intermetallics including half and full Heusler compounds.