Epitaxial Strain Engineering for High-Temperature Ferromagnetic Iron Germanide Alloy

The FeGe alloy has emerged as an exciting platform for exploring a variety of exotic quantum states, owing to the intricate intertwining of lattice, orbital charge, and spin degrees of freedom. However, either the extreme rarity of suitable candidates or the low Curie temperature (<i>T</i>_C) inevitably poses obstacles to practical applications. In this work, we have successfully synthesized single-crystalline FeGe alloy nanowires (NWs) on a c-plane Al₂O₃ substrate through a straightforward chemical vapor deposition (CVD) process. The relatively significant lattice mismatch at the FeGe/Al₂O₃ interface results in the compressed hexagonal lattice modification of FeGe. Remarkably, FeGe NWs exhibit ferromagnetic properties with <i>T</i>_C values as high as ∼730 K, whereas the bulk material displays antiferromagnetic ordering. Density functional theory calculations reveal that lattice compression boosts the magnetic moment of iron atoms, thereby stabilizing ferromagnetic states. These findings offer a pivotal case study for designing emergent magnetic properties via a spin-lattice coupling strategy.