Structure-Induced Ferromagnetic Stabilization in Free-Standing Hexagonal Fe1.3Ge Nanowires

Single-crystalline free-standing hexagonal Fe1.3Ge nanowires (NWs) are synthesized for the first time using a chemical vapor transport process without using any catalyst. Interestingly, Fe1.3Ge NWs are found to be ferromagnetic at room temperature, while bulk Fe1.3Ge has the lower critical temperature of 200 K. We perform first-principles density functional calculations and suggest that the observed strong ferromagnetism is attributed to the reduced distances between Fe atoms, increased number of Fe−Fe bonds, and the enhanced Fe magnetic moments. Both experimental and theoretical studies show that the magnetic moments are enhanced in the NWs, as compared to bulk Fe1.3Ge. We also modulate the composition ratio of as-grown iron germanide NWs by adjusting experimental conditions. It is shown that uniaxial strain on the hexagonal plane also enhances the ferromagnetic stability.