In γ-Fe₂MnGa Heusler alloy do Fe and Mn sublattices magnetically couple parallel or antiparallel at low temperatures?

Bulk and local magnetic properties of the polycrystalline γ-Fe₂MnGa Heusler alloy have been studied using X-ray diffraction, magnetization measurements and zero-field and in-field Mössbauer spectroscopy. X-ray diffraction data indicate stabilization of a L1₂-type structure and no structural phase transformation in the temperature range 30-300 K. While Mn atomic magnetic moments order magnetically well above 300 K according to magnetization data, ⁵⁷Fe Mössbauer spectroscopy suggests that the Fe-sublattice ordering temperature is ca. 220 K, when it couples antiparallel to the Mn-sublattice. Large vertical (magnetization-axis) and horizontal (field-axis) magnetization loop shifts are observed in field-cooling process (up to 70 kOe); these effects may be associated with magnetic frustrated state that occurs by interaction of the two sublattices.