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 $1200{}^{\circ }\mathrm{C}$ and from 30 GPa to 60 GPa. The compound crystallizes in the cubic $P{4}_{1}32$ space group with $\beta$-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 $A13-{\mathrm{Fe}}_2{\mathrm{Mg}}_3$ 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.

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• Equations of state
• High-pressure studies
• Phase diagrams
• Phase transitions
• Intermetallic compounds
• Solid solutions
• First-principles calculations
• X-ray diffraction