Two-Dimensional Superdegeneracy and Structure−Magnetism Correlations in Strong Ferromagnet, Mn₂Ga₅

Abstract

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 Mn2Hg5-type structure, exhibits a saturated magnetic moment of 2.71 muB per formula unit with T(C) approximately = 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.

Synthesis and magnetism of single-phase Mn-Ga films

“…All three M(T) curves have single magnetic transitions (ferrimagnetic to paramagnetic). The Curie temperature (T c ) for the Mn 2 Ga 5 phase is 435 K, close to the reported value, 9 whereas that for the Mn 2 Ga (T c ¼ 679 K) and Mn 3 Ga (T c ¼ 798 K) phases are much higher than that of Mn 2 Ga 5 . These high values of T c compare well with those reported for corresponding bulk ingot and melt-spun ribbon samples.…”

“…15 However, the saturation magnetizations of these Mn-Ga films are smaller than those reported for their bulk counterparts. 5,9 The low M s in the films may be caused by the significant structural disorder.…”

“…1(a) and 1(b), the diffraction peaks for the Mn 2 Ga 5 and Mn 2 Ga films can be indexed with the standard pattern for their tP14 and tP2 crystal structures. 9,10 The XRD pattern of Mn 3 Ga indicates that the film has crystallized into the hexagonal hp8 structure, Fig. 1(c).…”

“…7,8 The observed high coercivity has been attributed to the presence of an unidentified secondary phase which pins the domain walls of the main Mn 2 Ga 5 phase. Recently, a large net magnetization of about 1.36 l B /Mn has been reported for a Mn 2 Ga 5 button annealed at 773 K. 9 Our interest is to investigate structural, magnetic, and electron-transport properties of single-phase Mn 2 Ga 5 , Mn 2 Ga, and Mn 3 Ga films and compare their properties with those of the related compounds prepared by different methods. 1,5 In this paper, we present our experimental investigation on the crystal structure, magnetic, and electron-transport properties of e-beam evaporated Mn 2 Ga, Mn 3 Ga, and Mn 2 Ga 5 films.…”

Phase Formation of a Solid-Liquid Mn–Ga Diffusion Couple under a Magnetic Field

“…and T C = 450 K, respectively. 22) Therefore, an Mn Ga combination may be an interesting system for investigating the effect of a magnetic field on atomic diffusion in a metal. However, to the best of our knowledge, there have been no detailed reports on the effects of a magnetic field on the MnGa reaction or atomic diffusion.…”