Two-dimensional superdegeneracy and structure-magnetism correlations in strong ferromagnet, Mn₂Ga₅

The ferromagnetic intermetallic compound Mn₂Ga₅ has been synthesized and characterized by single-crystal X-ray diffraction study and by magnetic property measurements. The compound, with the Mn₂Hg ₅-type structure, exhibits a saturated magnetic moment of 2.71 μ_B per formula unit with T_C ≈ 450 K. The electronic structure of the compound was analyzed by employing FPLO, LMTO, and the extended Hückel tight-binding calculations. The nonmagnetic electronic structure of Mn₂Ga₅ reveals remarkably flat degenerate (superdegenerate) bands in the vicinity of the Fermi level but only in the a*b*-plane of the Brillouin zone. The resulting high density of the states at the Fermi level, DOS(E_F), is consistent with the Stoner condition for the observed itinerant electron ferromagnetism. Detailed orbital analysis shows an intriguing structure-magnetism correlation, as the superdegeneracy is found to be a consequence of the unique atomic arrangement and bond angles in the structure.