Pressure-induced anomalous properties of Laves phase and orthorhombic phase of YFe2

Abstract

The magnetic, lattice dynamical, and elastic properties of the Laves phases (C14, C15, and C36) and the orthorhombic (Imma) phase of YFe₂ were investigated under ambient and high pressures using first-principles calculations. Below 86 GPa, the C15 and Imma phases exhibit higher thermodynamic stability compared to the C14 and C36 phases. However, the C14 phase becomes the most stable structure when the pressure exceeds 86 GPa. At ambient pressure, all Fe atoms in the C15, Imma, and C14 phases exhibit magnetic moments of approximately 2 μ_B, while Y atoms possess negative magnetic moments of about −0.5 μ_B, resulting in ferrimagnetism in all four phases. Notably, in the C36 structure, the magnetic moments of Fe atoms at the 6h site are antiparallel to those at other sites, with three reversals observed under pressures from 0 to 8 GPa. Elastic and dynamical analyses indicate that the C36 phase becomes unstable near 10 GPa, while the C14 phase is elastically unstable near 5 GPa but dynamically stable and brittle. The system shows negligible shear and compression resistance near these pressures but exhibits ductility at other pressure ranges. These findings provide new insights into the pressure-dependent properties of YFe₂, offering guidance for its potential applications under varying pressure conditions.