Ab initiostudy of ferromagnetism in edged iron nanowires under axial strain

Abstract

We perform first-principles simulations of the magnetic and electronic properties of ferromagnetic (FM) body-centered cubic (bcc) iron nanowires with characteristic sharp edges consisting of (110) and (1$\overline{1}$0) surfaces and their response to mechanical strain. An enhanced magnetic moment of 2.83${\ensuremath{\mu}}_{B}$ is obtained at the edge of the FM nanowire. This enhancement originates from rearrangement of $d$ electrons from the minority-spin ${t}_{2g}$ state to the majority-spin ${t}_{2g}$ state due to a significant reduction in the number of nearest-neighbor atoms at the edge. The FM phase is the most energetically favorable phase in the nanowire even under relatively high axial strains, whereas the corresponding bulk material exhibits a FM-to-antiferromagnetic transition under the same loading conditions. During tension, a discontinuous change in the magnetic moment is observed at the surface and inside the nanowire due to a bcc--face-centered-cubic structural transition. In contrast, the magnetic moment at the edge is insensitive to applied strain. This is because the majority-spin state is fully occupied at the edge, which restricts the ${t}_{2g}$-${e}_{g}$ electron rearrangement to just the minority-spin state.