Large saturation moment and high ferromagnetic transition temperature in a structurally disordered inverse Heusler alloy Fe2RuGe
arXiv:2306.14831
Abstract
We report the successful synthesis of a new 4 based polycrystalline inverse Heusler alloy FeRuGe by an arc melting process and have studied in detail its structural, magnetic and transport properties complemented with first principle calculations. X-ray and neutron diffraction, Extended X-ray Absorption Fine Structure and Fe Mössbauer spectroscopic studies confirm the single phase nature of the system where the Fe and Ru atoms are randomly distributed in the 4 and 4 Wyckoff positions in a ratio close to 50:50. The formation of the disordered structure is also confirmed by the theoretical energy minimization calculation. Despite the random cross-site disorder of Fe and Ru atoms, magnetic measurements suggest not only a high Curie temperature of 860\,K, but also a large saturation magnetic moment 4.9\, per formula unit at 5\,K, considerably exceeding the theoretical limit (4\, per formula unit) predicted by the Slater-Pauling rule. Only a few Fe-based inverse Heusler alloys are known to exhibit such high Curie temperatures. Neutron diffraction analysis coupled with the isothermal magnetization value indicates that the magnetic moments in FeRuGe are associated with Fe-atoms only, which is also confirmed by Mössbauer spectrometry. Interestingly, in comparison to the cubic or hexagonal phase of the parent compound, FeGe, the Curie temperature of FeRuGe has increased significantly despite the substitution of the nonmagnetic, yet isoelectronic element Ru in this structurally disordered compound. Our theoretical calculation reveals that the large Fe moment (/Fe) on the 4 site can be attributed to a charge transfer from this Fe site towards its Ru neighbours. Such a substantial increase in magnetic moment due to electron charge transfer has not previously been reported in a Heusler alloy system.