Determine the magnetic ground-state ordering of MgFe6Ga6

Determine the magnetic ground-state ordering of MgFe6Ga6 among the competing θ = 120° spin-spiral states, AFM2 order, and the long-period AFM6 collinear superstructure, whose relative energies depend on the exchange-correlation treatment and lie within the resolution of the calculations.

Background

MgFe6Ga6 exhibits several nearly degenerate magnetic configurations: a finite-angle spin spiral with an approximately 120° rotation between every two Fe Kagome layers, the long-period AFM6 collinear stacking, and AFM2 order. PBE calculations favor the spin-spiral state, whereas LDA favors AFM2, with the competing states separated by only approximately 0.5 meV per Fe atom.

Because the predicted ordering changes with the exchange-correlation functional and the energy differences are comparable to the numerical uncertainty, the calculations do not establish which configuration is the true zero-temperature magnetic ground state. Resolving this problem is important for identifying the magnetic structure and for interpreting possible finite-temperature competition among the states.