Fe 2 Mg 3 stabilization and solid-solution preliminary observations in the Fe-Mg system at high pressure and high temperature

High-pressure, high-temperature synthesis is a valuable technique for the investigation of binary systems because it enables the stabilization of new phases that are metastable at ambient pressure and temperature. Because of its low bulk modulus, the atomic radius of Mg undergoes a large shrinkage above the GPa range, which can lead to the stabilization of potential new structures with other transition-metal (TM) elements. The present study reports on the synthesis and characterization of a Mg–Fe intermetallic phase in aser-heated diamond anvil cells (LH-DAC) on the ID27 beamline of the ESRF, above 1200◦Candfrom30GPato60GPa. The compound crystallizes in the cubic P4132 space group with β-Mn structure as a prototype (Strukturbericht designation A13). Several isobaric heating experiments as well as a temperature-controlled decompression were performed on this A13 phase, observed to be stable in two different compositions of Fe–Mg samples obtained by physical vapor deposition (PVD) (48 at.% Mg and 68 at.% Mg). Additional first-principles calculations on ordered and disordered phases were also performed to support the experimental work. A thermal equation of state of the A13−Fe2Mg3 phase is proposed, as well as a diagrammatic interpretation, taking into account the experimental results with the corresponding binary phase diagrams on the Mg-rich side.