Results 1 - 10 of 1731
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[en] Highlights: • A new Heusler alloy V2CuAl with Hg2CuTi-type structure has been developed. • The conducting character is shown by the majority and minority spin band structures calculations. • The magnetic moments of V(1) atom and V(2) atom indicated that the alloy is a ferromagnet. - Abstract: In this article, a new Heusler alloy V2CuAl with Hg2CuTi-type structure has been obtained by first-principles calculations. The electric structure and magnetic performance of the alloy have also been investigated. The results show that the alloy has a total magnetic moment of 0.87μB per unit cell obtained by first-principles calculations. In addition, the conducting character and metal property are presented by the majority and minority spin band structures calculations. Furthermore, the magnetic moments of V(1) atom and V(2) atom are 0.36μB and 0.38μB, respectively, indicating that the alloy is a ferromagnet
[en] The half-metallic and elastic properties of Mn2IrAl full-Heusler compound was investigated using WIEN2k code. The ferromagnetic (FM) states were compared non-magnetic (NM) states in Hg2CuTi and Cu2MnAl structures for determined which phase was the most stable. The FM phase in Hg2CuTi structure was observed more stable energetically. The computed results showed that the spin-up (majority) electrons of Mn2IrAl compound had metallic feature while spin-down (minority) electrons had semiconduction behavior with an energy gap of 0.43 eV. According to calculated Cij elastic constants, Mn2IrAl compound was elastically stable as it provides stability conditions and it was a ductile material. Finally, Mn2IrAl compound was found true half-metallic ferromagnet within 2 μ B/f.u. (paper)
[en] First principles calculation has been employed to investigate the physical properties and thermodynamic properties of XCrBi (X = Hf, Ti and Zr) half-Heusler alloys. The half Heusler alloys TiCrBi and ZrCrBi studied are found to possess half-metallic character except HfCrBi showing metallic behaviour in both spin up and spin down channel. The Slater-Pauling rule is uesd to predicted the total magnetic moment of 3μB which confirmed the values from calculation. All half Heusler alloys are mechanically and thermodynamically stable. (paper)
[en] Complete text of publication follows. We have performed x-ray absorption near edge structure (XANES) study on a series of Heusler compounds Ni2+xMn1-xGa (x=0.0 ∼ 0.24) in order to investigate the effect of substitution on the electronic properties and its correlation to the structural (martensitic) transformation. Our XANES results of Ni and Mn K-edge indicate that the increase in Ni concentration causes an increased Ni valance from 2+ and a decreased Mn valence from 3+. The distinct difference in the spectral shapes of the K-edge spectra shows that a structural transformation occurs at around x=0.14 in room temperature, which is consistent with the reported structural measurements. From the results of Ni and Mn L2,3-edge spectra we observe, as x increases, an increasing charge transfer from Ni 3d to 4p orbital, which is associated with a more stable local structure. This work is financially sponsored by National Science Council of Republic of China under grand number NSC 97-2112-M-032-005-MY3.
[en] Te-based half-Heusler systems are studied by first-principle calculations to search for alloys with stable half-metallic properties. We found that CoMnTe and FeMnTe are the most robust half-metallic (HM) ferromagnetic alloys among the 90 studied alloys, with HM gaps of 0.42 and 0.61 eV, respectively, larger than that of any Heusler or half-Heusler alloys reported in the literature. The half-metallicity of CoMnTe and FeMnTe is found to be robust under large in-plane strains, which makes them suitable for practical spintronic device applications. - Highlights: • We found a robust ferromagnetic alloy (FeMnTe) of half-metallic gap at 0.61 eV from 90 half-Heusler alloys. • The half-metallic property of FeMnTe is robust with respect to the in-plane strain. • Strong d–d hybridization and proper choice of s–p elements are suggested for larger half-metallic gaps in half-Heusler alloys
[en] Complete text of publication follows. It has been reported that the structural, thermal and electronic properties of the Heusler-type compound Fe2VSi can be markedly modified by partially substituting Si with Al. The variations of the physical properties are related to the change in the electronic structure due to the hetero-valence doping of Al for Si. We have performed x-ray absorption near edge structure (XANES) study on a series of polycrystalline Fe2VSi1-xAlx (x=0∼0.25) samples to study the electronic structure of these materials. Our Fe K-edge and V K-edge XANES results indicate that the Al doping does not affect the valence of Fe or V, neither has it affected the degree of hybridization between Fe and V. Alternatively, the Al 3p-Fe 3d, and Al 3p-V 3d hybridizations are highly affected by the doping level. From Fe L2,3-edge XANES results we observe a systematic variation on the Fe d unoccupied states, which is correlated with the reported resistivity and thermal power measurements. This work is financially sponsored by National Science Council of Republic of China under grand number NSC 97-2112-M-032-005-MY3.
[en] Formation of the Ni2MnSn Heusler alloy by solid state reaction from elemental powders was investigated. The solid state reaction was conducted in a planetary ball mill under argon atmosphere up to 28 h of milling. During the milling, after selected intervals samples were collected and studied by X-ray diffraction to record phase changes. After 16 h of milling a two phase mixture (Ni2MnSn with B2 structure and NiMnSn with C1b structure) was found. Further, the thermal stability of the samples was investigated, and phase precipitation was found. The formed phases are ordered Full Heusler (L21) and Ni3Sn2. The formation temperature and their amount evolution versus temperature and milling time is discussed. An inversion of the formation temperature was found for the L21 and Ni3Sn2 phase, during the DSC study, in relation with the milling time. For the B2 compound a stability range on temperature was identified (from 25 to 300 °C), as well as for the L21 and Ni3Sn2 phases (from 400 to 600 °C) in the case of 28 h milled sample. The milled and annealed sample exhibit nanocrystalline state, formation mechanism under temperature was concluded to be by precipitation. - Highlights: • Mechanosynthesis of Ni2MnSn Heusler alloy from elemental powder is studied. • After 28 h of milling the phases are Ni2MnSn - B2 (90 % wt) and NiMnSn - C1b. • The Heusler B2 phase is stable up to 300 °C. • The B2 phase decompose over 300 °C into L21 structure and Ni3Sn2 phase. • L21 structure and Ni3Sn2 phase formation temperatures is inverted by milling.
[en] We report the magnetism and magnetic entropy change in the Mn-rich Ni48Mn39Sn13 Heusler alloy system. The excess Mn content stabilizes the cubic austenite phase at room temperature. The shift of Martensitic transition temperature to low temperature with the application of higher magnetic field. A magnetic entropy change (SM) of 12.12 Jkg-1K-1 has been achieved for a field change of 5 T for this alloy. (author)