Epitaxial Stabilization of Ferromagnetism in the Nanophase of FeGe

Epitaxial nanocrystals of FeGe have been stabilized on Ge(111). The nanocrystals assume a quasi-one-dimensional shape as they grow exclusively along the ⟨11̅ 0⟩ direction of the Ge(111) substrate, culminating in a compressed monoclinic modification of FeGe. Whereas monoclinic FeGe is antiferromagnetic in the bulk, the nanowires are surprisingly strong ferromagnets below ∼200  K with an average magnetic moment of 0.8μ_B per Fe atom. Density functional calculations indicate an unusual stabilization mechanism for the observed ferromagnetism: lattice compression destabilizes the antiferromagnetic Peierls-like ground state observed in the bulk while increased p-d hybridization suppresses the magnetic moments and stabilizes ferromagnetism.