The binary compound V3Ga can exhibit two near-equilibrium phases, the A15 structure that is superconducting and the Heusler D03 structure that is semiconducting and antiferromagnetic. Density functional theory calculations show that these two phases are nearly degenerate, being separated in energy by only ±10 meV/atom. Our magnetization measurements on bulk-grown samples show antiferromagnetism and superconducting behavior below 14 K. These results indicate the possibility of using V3Ga for quantum technology devices exploiting the co-existence of superconductivity and antiferromagnetism in a dual-phase material.

The effects of post-synthesis annealing temperature on arc-melted samples of Fe3Ga4 has been studied to investigate changes in crystallographic and magnetic properties induced by annealing. Results show a significant trend in the evolution of the (incommensurate spin density wave) ISDW-FM (ferromagnetic) transition temperature as a function of the refined unit cell volume in annealed samples. Strikingly, this trend allowed for the tuning of the transition temperature down to roomtemperature (300 K) whilst maintaining a sharp transition in temperature, opening the door to the use of Fe3Ga4 in functional devices. Crystallographic analysis through Rietveld refinement of highresolution x-ray diffraction data has showed that arc-melted stoichiometric Fe3Ga4 is multi-phase regardless of annealing temperature with a minor phase of FeGa3 decreasing in phase fraction at higher annealing temperature. In order to validate the trend in ISDW-FM transition temperature with regard to unit cell volume, high pressure magnetometry was performed. This showed that the FM-ISDW (∼ 68 K) and ISDW-FM (∼ 360 K) transition temperatures could be tuned, increased and decreased respectively, linearly with external pressure. Thus, external pressure and the ensuing crystallographic changes minimize the temperature range of the stability of the ISDW pointing toward the importance of structural properties on the mechanism for the formation of the intermediate ISDW phase. These results show how this model system can be tuned as well as highlighting the need for future high-pressure crystallography and related single crystal measurements to understand the mechanism and nature of the intermediate ISDW phase to be exploited in future devices.

The Co-rich end of the Co–Tb binary phase diagram (CoxTb1−x, x = 0.66–0.82) has been investigated to understand the phases which form in the bulk and how they interact to yield magnetic behavior which has been reported to be ideal for use in spintronic devices. This work shows that the phases and phase fractions present across this composition range follow those predicted by the binary phase diagram, and all compounds in this composition range are multiphase. Magnetic measurements show similar behavior in this composition range to related thin film work, and we attribute the observed behavior to the respective binary phases present in each compound. Ideal magnetic behavior of minimized magnetic saturation and maximized coercivity is observed in the range of x=0.78−0.80 related to the majority phase Co7Tb2 in these two compounds. High pressure magnetic measurements show magnetic saturation and coercivity at 300 K change little with respect to external pressure. The extension of the synthesis of these binaries into the bulk allows for specific binary phases to be targeted and analyzed for consideration in future devices.

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