Pressure-induced disruption of the local environment of Fe-Fe dimers inFeGa3accompanied by metallization

Abstract

The semiconducting gap in the $\mathrm{FeG}{\mathrm{a}}_{3}$ intermetallic originates from $\mathrm{Fe}(3d)/\mathrm{Ga}(4p)$ hybridization. Pressures of 15--20 GPa initiate a disruption of this semiconducting tetragonal $P{4}_{2}/mnm$ structure and an emergence of a high-pressure metallic phase, estimated to be fully stabilized just beyond \ensuremath{\sim}35 GPa. An accompanying pronounced \ensuremath{\sim}17% volume collapse occurs at the structural transition. The high-pressure metallic phase has a ${T}^{1/2}$ temperature dependence of the resistivity below its minimum at 8--12 K, symptomatic of disorder. There is a corresponding weak high-temperature dependence of the resistivity and resultant broad maximum at \ensuremath{\sim}250 K to yield ``bad-metal'' values of \ensuremath{\sim}0.5 m\ensuremath{\Omega} cm at room temperature. This is shown to signify that the high-pressure phase is a low carrier density metal on the verge of an Anderson transition. Ga $K$-edge absorption spectroscopy and Fe M\ossbauer spectroscopy local probes indicate that the atomic disorder stems from a pressure-instigated rearrangement of the Ga sublattice at the structural transition.