Mixed structural face-centered cubic and body-centered cubic orders in near stoichiometric Fe2MnGa alloys

Abstract

Magnetic and transport properties of near stoichiometric metastable FexMnyGaz alloys (46 ≤ x ≤ 52, 17 ≤ y ≤ 25, 26 ≤ z ≤ 30) with face-centered cubic (FCC), body-centered cubic (BCC), and two-phase (FCC + BCC) structures are investigated. The experimental results are analyzed in terms of first-principles calculations of stoichiometric Fe2MnGa alloy with the L21, L12, and the tetragonally distorted L21 structural orderings. It is shown that the pure BCC and FCC phases have distinct magnetic and transport properties. Two-phase Fe2MnGa alloys have magnetic and transport properties typical of the mixed BCC and FCC phases. Among the investigated alloys, Fe46Mn24Ga30 has a martensitic transformation accompanied with significant changes of its magnetic and transport properties.

Influence of Oxidation on Electrical Properties of Compacted Cu Nanopowders

“…These results are consistent with those [4] where semiconducting behavior associated with presence of copper and manganese oxides was reported for compacted specimens of highly dispersed Cu-13.1 % Mn-12.6 % Al powder. It should be noted that in case of disordered intermetallic alloys, semiconducting behavior can be attributed to strong atomic scattering, which results in quantum interference effects such as a weak localization or hopping conductivity [7–10]. Nevertheless, analysis of all collected experimental results allowed authors to conclude that the Cu-13.1 % Mn-12.6 % Al-compacted powders comprised of ordered and disordered phases demonstrated semiconducting behavior owing to appearance of oxide layer on the surface of particles rather than by other reasons [4].…”

Magnetic and Magneto-Optical Properties of Fe75−xMn25Gax Heusler-like Compounds

“…The low-field magnetization confirmed expected high Curie temperatures in all compounds close to stoichiometry. The high Curie temperature phase can be identified from the literature as fcc phase [12,13]. The highest temperature, about 760 K, was measured for the sample (Fe50) closest to stoichiometry.…”

“…This agreed with MOKE observation at room temperature. According to Kudryavtsev, the matrix phase with a low Curie point is the disordered bcc phase [12,13].…”

“…Heusler Fe-Mn-Ga compounds have been proposed as good candidates for new MSM material [10] as they have a much higher Curie point than Ni-Mn-Ga. However, it was found very soon that martensitic transformation is not a universal feature, and it occurs only in some particular compositions [11][12][13][14]. Apart from thermally induced transformation [15], even the field-induced transformation was observed for Fe 2 MnGa by Zhu et al [16].…”

“…Overall, the magnetic state is not well understood even for stoichiometric Fe 2 MnGa. Despite the mixed structural order of fcc-and bcc-like phases in near stoichiometric Fe 2 MnGa, Kudryavtsev et al were able to determine its electronic and optical properties and compare it with ab initio calculations [13,20]. However, the published results are incomplete as the most studied compositions are close to the stoichiometric Fe 2 MnGa compound.…”