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Abstract: The martensitic transformation in Heusler alloy Mn2PtIn has been investigated by first-principles calculations and experimental studies. Theoretical calculation reveals that, in Mn2PtIn, a transition from cubic structure to tetragonal one is favorable in energy. This has been confirmed by following experimental studies. At room temperature, Mn2PtIn crystallizes in a tetragonal structure of the space group I-4m2. And a transition from tetragonal to cubic Heusler phase occurs at 638K. Mn2PtIn is a ferrimagnet in both austenitic and martensitic phases. Its magnetic properties are mainly determined by the antiparallel aligned Mn spin moments. These findings can greatly enlarge our scope of discovering new FSMAs in Heusler alloys containing 4d and 5d elements. [Copyright &y& Elsevier]

Abstract: The electronic structure and magnetism of Heusler alloys Mn2NiGe and Ni2MnGe have been studied by first-principles calculations. The possible non-modulated tetragonal martensitic transformation in them has been predicted. For both Mn2NiGe and Ni2MnGe, the tetragonal martensitic phase is lower in energy compared with the cubic austenitic phase. In Ni2MnGe, the martensitic transformation follows the conservation of volume. But in Mn2NiGe, a small contraction of the martensitic cell volume is predicted. The energy difference ΔE between the martensitic and austenitic phase is −8 meV/cell in Ni2MnGe and −80 meV/cell in Mn2NiGe, so it is more likely to observe martensitic transformation in Mn2NiGe or Heusler alloys with similar compositions. Ni2MnGe is found to be a ferromagnet, while Mn2NiGe is a ferrimagnet in which the Mn spin moments are in antiparallel coupling. [Copyright &y& Elsevier]

Mn2NiSb can exist in both ferromagnetic and antiferromagnetic states because there is only a small total energy difference between the two states. In its electronic structure, two different types of energy gaps exist and are close to the Fermi level. The relative position of the Fermi level to the gap determines the ferromagnetic or antiferromagnetic state. That is the origin of the magnetic instability in Mn2NiSb. A 70% decrease of the total moment is predicted between the ferromagnetic and antiferromagnetic Mn2NiSb. [Copyright &y& Elsevier]

Abstract: The electronic structure and magnetic properties of new Fe-based Heusler alloys Fe2TiZ (Z=Ga, Ge, As, In, Sn and Sb) have been studied by first-principles calculations. In these alloys, the 24-electron Fe2TiGe, Fe2TiSn are nonmagnetic semiconductors and other compounds are all ferrimagnetic metals. Fe2TiAs and Fe2TiSb are predicted to be half-metals with 100% spin polarization. The spin polarization ratio in Fe2TiGa and Fe2TiIn is also quite high. The calculated total moment for Fe2TiAs and Fe2TiSb is 1μB, which is mainly determined by the Fe partial moment. The half-metallicity of Fe2TiSb is stable under lattice distortion. The spin polarization of Fe2TiSb is found to be 100% for the lattice variation in a range of 5.6–6.1Å, which is attractive in practical applications. [Copyright &y& Elsevier]

Abstract: The origin of the Slater–Pauling curve M t =Z t −28 (Here M t is the total spin moment and Z t is the number of valence electrons) in half-metallic Heusler alloys Mn2CuZ (Z=Ge and Sb) has been studied in detail. In Mn2CuZ the half-metallic gap has a similar origin like half-Heusler alloys. The Cu atom acts as an electron “donator” in Mn2CuZ, which contributes five d-electrons to the minority spin band of Mn2CuZ. So there are 14 valence electrons in the minority band of Mn2CuZ below the Fermi level. This is the origin of the S–P curve M t =Z t –28. Finally, it is found that, by partial doping of Cu to the vacant site of half-metallic half-Heusler alloys, the magnetic moments of these can be tuned without destroying the half-metallicity. This can be a possible way to design new half-metals. [Copyright &y& Elsevier]

Abstract: The Slater–Pauling behavior and half-metallic properties of full-Heusler alloys Mn2CuZ (Z=Ge and Sb) have been studied by first-principles calculations. It is found that the total spin moment (Mt ) and the number of valence electrons (Zt ) follow a Slater–Pauling rule of Mt = Zt −28 rather than Mt = Zt −24 in normal Heusler alloys. Mn2CuSb is predicted to be a half-metal at equilibrium lattice constant and Mn2CuGe is also half-metallic with a small expansion of the lattice. Mn2CuGe and Mn2CuSb are both ferrimagnets with total spin moment of +0.97μB/f.u. and +2.00μB/f.u., respectively. Considering Mn2CuGe and Mn2CuSb have 29 and 30 valence electrons, the S-P curve of Mt = Zt −28 works quite well. This different S-P rule is strongly related to the low-lying Cu states and the weak hybridization between the d states of Cu and Mn. [Copyright &y& Elsevier]

Abstract: Quaternary Heusler alloys Fe1.5M0.5CoSi with M=V, Cr, Mn and Fe have been investigated theoretically and experimentally. All of these samples crystallize in the ordered Heusler-type structure. The calculated electronic structure shows a pseudogap around E F in the minority spin states of Fe2CoSi. With the substitution of low-valent atoms for Fe, the majority antibonding peak is shifted to higher energy and a minority gap around the Fermi level is opened. High spin polarization ratio is obtained in Fe1.5M0.5CoSi (M=V, Cr, Mn) alloys. The calculated total spin moments decrease with decreasing number of valence electrons and follow the Slater–Pauling curve, which agree with the experimental results well. The Curie temperature decreases as M atom varies from Fe to V, but is always higher than 650K, which is suitable for technical applications. [Copyright &y& Elsevier]

The effect of boron substitution for Sb in the Heusler alloys Ni50Mn36.5Sb13.5− x B x (x =0, 0.5, 1.0, 1.5) has been studied. The substitution with B reduces the Curie temperature of both the martensite and austenite phases. The saturation magnetization M s decreases monotonically with increasing B content. The doping of B increases the martensitic transformation temperature effectively. When x =1.0 and 1.5, an orthorhombic four-layered (4O) martensite is observed at room temperature. [Copyright &y& Elsevier]

Abstract: The electronic structure and magnetism of the Heusler alloy Mn2NiAl have been studied by first-principles calculations. It is found that the phase transformation from the cubic to the tetragonal structure lowers the total energy, indicating that the martensitic phase is more stable and that a phase transition from austenite to martensite may happen at a lower temperature. Thus, ferromagnetic shape memory effect can be expected to occur in Mn2NiAl or in alloys of similar composition. Mn2NiAl is a ferrimagnet in both the austenitic and martensitic phases. The total spin moments are 1.48 and 1.14μB/f.u. for the austenite and martensite, respectively. Because the contribution of Ni to the total moment is small, the total moment is mainly determined by the antiparallel aligned Mn(A) and Mn(B) spin moments. [Copyright &y& Elsevier]

Abstract: The magnetic properties and electronic structure of Mn2NiZ (Z=In, Sn, Sb) have been studied. The magnetic structure of these alloys is mainly determined by the main-group element Z instead of the distance between the Mn atoms. Electronic structure calculations suggest that Mn2NiIn and Mn2NiSn are both ferrimagnets with antiparallel alignment between the Mn moments. But this antiferromagnetic coupling is weakened by the increasing number of valence electrons of the Z atoms. When it comes to Mn2NiSb, a ferromagnetic coupling between the Mn atoms is observed. Mn2NiSn and Mn2NiSb have been synthesized successfully. Their M s at 5K agree well with the theoretical value. [Copyright &y& Elsevier]

Abstract: The effect of doping on the half-metallicity and magnetism of Co2− x Cr x CrAl (x=0–1) alloys was studied by full-potential linearized-augmented plane wave (FLAPW) calculations. With increasing Cr content, a transition from the half-metallic ferromagnet (HMF) to the half-metallic completely compensated ferrimagnet (HMCCF, also called half-metallic antiferromagnet) is observed. The calculations indicate that Co2− x Cr x CrAl alloys are half-metallic within the whole range studied. Substitution of Cr for Co leads to a large antibonding peak above E F in the majority-spin band, but still keeps the energy gap in the minority-spin band. The size of the gap is mainly determined by the density of states (DOS) of atoms at the (A, C) sites. With increasing Cr content, the total spin moment decreases linearly from 3μ B/f.u. to zero, which obeys the Slater–Pauling curve quite well. The spin moment of Cr at the C site is antiferromagnetically aligned with the magnetic moments of the Cr (B) and the Co atoms. This antiferromagnetic coupling causes a monotonic decrease of the total magnetic moment. [Copyright &y& Elsevier]

Abstract: The effect of doping with Cr on the electronic structure and magnetism of Co3Al has been studied by density functional calculations. It has been found that the Cr atom has a strong site preference for the B-site in Co3Al. With the substitution of Cr for Co, the total densities of states (DOS) change obviously: A DOS peak appears at E F in the majority spin states and an energy gap is opened in the minority spin states. The effect of Cr in Co3Al is mainly to push the antibonding peak of the Co (A,C) atoms high on the energy scale and to form the energy gap around E F, and also to contribute to the large DOS peak at E F in the majority spin direction. The calculations indicate a ferromagnetic alignment between the Co and Cr spin moments. The calculated total magnetic moment decreases and becomes closer to the Slater–Pauling curve with increasing Cr content. This is mainly due to the decrease of the Co (A,C) spin moments. At the same time, the moments of Co (B) and Cr (B) only change slightly. [Copyright &y& Elsevier]

Abstract: The electronic structure of the highly ordered alloy Cr3Co with the DO3 structure has been studied by FLAPW calculations. It is found that the ferrimagnetic state is stable and that the equilibrium lattice constant of Cr3Co equals 5.77Å. A large peak in majority spin density of states (DOS) and an energy gap in minority spin DOS are observed at the Fermi level, which results in a high spin polarization of 90% in the ordered alloy Cr3Co. The total magnetic moment of Cr3Co is 3.12μ B, which is close to the ideal value of 3μ B derived from the Slater–Pauling curve. An antiparallel alignment between the moments on the Cr (A, C) sites and the Cr (B) sites is observed. Finally, the effect of lattice distortion on the electronic structure and on magnetic properties of Cr3Co compound is studied. A spin polarization higher than 80% can be obtained between 5.55 and 5.90Å. With increasing lattice constant, the magnetic moments on the (A, C) sites increase and the moments on the (B, D) sites decrease. They compensate each other and make the total magnetic moment change only slightly. [Copyright &y& Elsevier]

Abstract: First-principles FLAPW calculations were performed on the Mn2CrZ (Z=Al, Ga, Si, Ge and Sb) alloys. Based on these results we predict two half-metallic ferromagnets (HMFs) namely Mn2CrAl and Mn2CrSb, and also find an energy gap in Mn2CrGa which lies near the Fermi level. The energy gap lies in the majority spin band for Mn2CrAl and Mn2CrGa, whereas in the minority one for Mn2CrSb. The calculated total spin magnetic moments M t cal are −1μ B per unit cell for Mn2CrAl and Mn2CrGa, +1μ B per unit cell for Mn2CrSb and zero for Mn2CrSi and Mn2CrGe, which agree with the Slater–Pauling rule. The calculation indicates a large and localized magnetic moment of Cr at B site. This is meaningful for searching for new half-metallic antiferromagnets in Heusler alloys. The magnetic moment of Cr is found to increase with increasing atomic number of Z and is antiparallel to that of Mn. The change of Mn and Cr spin moments compensates each other and keeps the total spin moment as an integer when the Z atom is changed. [Copyright &y& Elsevier]

The site preference, electronic structure, magnetic properties and martensitic transformation in Heusler alloys Ni 2 CoZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) have been investigated by first-principles calculations. Different from literature, it is found that these Ni 2 CoZ alloys tend to form XA structure (Hg 2 CuTi-type), except for Ni 2 CoIn, in which L2 1 (Cu 2 MnAl-type) structure is preferable. Theoretical calculation reveals that the tetragonal martensitic phase has a lower total energy compared with the cubic austenitic phase, therefore, a structural transition from cubic to tetragonal is likely to happen in these Ni 2 CoZ alloys. The largest energy difference is observed in Ni 2 CoIn. It is interesting that Ni 2 CoSi is paramagnetic in austenitic state, while is ferromagnetic in martensitic state. This leads to a large change in the total moment, which is meaningful for the realization of magnetic field-induced martensitic transformation in this alloy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Electronic structure of quaternary Heusler alloys FeRuYZ was investigated. • New spin gapless semiconductors and half-metals were reported. • Rule between formation energy and mine group element Z was discussed. Abstract Phase stability, electronic structure and magnetic properties of the FeRu-based quaternary Heusler alloys, FeRuYZ (Y = Ti, V, Cr, Mn and Z = Al, Ga, In, Si, Ge, Sn), have been investigated theoretically. In one primitive unit cell, these alloys contain 24–26 valence electrons. The formation energy E f of FeRuYZ increases with increasing atomic number of Z when the Y or Z elements belong to the same group in the periodic table. And in the same period, group-IIIA Z element is not preferable for the stability of FeRuYZ compared with corresponding group-IVA element. This can be explained from the charge density difference. The 24-electron FeRu-based quaternary Heusler alloys are all paramagnets. Among them, FeRuTiSi (Ge, Sn) are all semiconductors with real band gap at the Fermi levels. These alloys may have potential applications as thermoelectric materials. High spin polarization ratio is observed in the 25-electron Heusler alloys, among which FeRuCrAl is predicted to have a 100% spin polarization ratio. The 26-electron FeRuCrSi is found to be a spin gapless semiconductor (SGS) with total spin moment of 2μ B. These materials can be interesting for the development of spintronic materials. The origin of SGS character in FeRuCrSi was discussed and compared with half-metallic Fe 2 CrSi, in which Ru and Fe are isoelectronic. These findings can help to design new SGSs in Heusler alloys. [ABSTRACT FROM AUTHOR]

• All-d-metal Heusler alloy Mn 2 PtTi is a promising new MSMA with high martensitic transformation temperature. • Large volume effect of 2.9% cell shrinkage occurs in Mn 2 PtTi during the martensitic transformation. • Electronic structure and magnetic properties of new all-d-metal Heusler alloys Mn 2 PtZ (Z = Sc, Ti and V) are investigated. The atomic ordering, electronic structure, magnetic properties and martensitic transformation of three new all-d-metal Heusler alloys Mn 2 PtZ (Z = Sc, Ti and V) have been investigated theoretically to discover new magnetic shape memory alloys (MSMAs). Depending on the different third transition metal element Z, Mn 2 PtSc and Mn 2 PtTi tend to form XA structure while Mn 2 PtV forms L2 1 structure. This difference is related to their DOS structures. Charge density difference calculations indicate enhanced d-d hybridization in these all-d-metal Heusler alloys. Mn 2 PtZ are all ferrimagnets with their Mn-Mn or Mn-V local spin moments antiparallel coupled. In these alloys, Mn 2 PtTi is a possible new MSMA with the energy difference ΔE M between the martensite and austenite as large as −262 meV/f.u., which indicates a high martensitic transformation temperature and is related to the Jahn-Teller effect in the electronic structure. A large volume effect of 2.9% cell shrinkage occurs during the martensitic transformation. All this makes Mn 2 PtTi a promising candidate for MSMAs with wide applications. [ABSTRACT FROM AUTHOR]

The equiatomic quaternary Heusler alloy FeRuCrSi was synthesized and its atomic ordering, magnetic properties and electronic structure were investigated experimentally and theoretically. The FeRuCrSi formed a single Heusler phase and had a lattice constant of 5.811 Å at room temperature. An L2 1 B-type disorder related to the random occupation of Fe and Ru at 4a and 4b sites was identified in the X-ray diffraction pattern. The Curie temperature of FeRuCrSi was 346 K and the saturation magnetization at 5 K was 1.84 μ B /f.u., which is smaller than the integral value of 2.00 μ B required for ideal spin gapless semiconductor character and is likely related to the L2 1 B-type disorder. First-principles calculations revealed that ordered FeRuCrSi with Y II -type structure had the lowest total energy at 0 K. However, the energy difference between it and the L2 1 B structure was only 0.09 eV/f.u., thus the L2 1 B disorder dominated in the experimental sample because of the enthalpy of mixing and the "freezing" of high-temperature disorder at room temperature. The Y II -type FeRuCrSi was a SGS with a half-metallic gap in the minority density of states (DOS) and a zero-width gap in the majority DOS. However, the L2 1 B-type disorder disturbed the SGS character by narrowing the two gaps. The total spin moment of ordered FeRuCrSi was 2.00 μ B /f.u., mainly determined by the antiparallel coupled Cr and Fe/Ru spin moments. However, the total moment was slightly reduced in L2 1 B-type FeRuCrSi. All this suggests that the possible L2 1 B disorder should be carefully considered when designing and synthesizing half-metals/SGS in Heusler alloys for spintronic applications. • Equiatomic quaternary Heusler alloy FeRuCrSi was synthesized successfully, which is a ferrimagnet with T C of 346 K and Ms at 5 K of 1.84 μ B /f.u. • FeRuCrSi experimental sample crystallizes in a partly disordered L2 1 B structure • L2 1 B disorder disturbs the spin gapless semiconductor character predicted in literature • Influence of L2 1 B disorder should be considered carefully in the design of Heusler alloys for spintronic applications [ABSTRACT FROM AUTHOR]

Two new all-d-metal Heusler alloys Mn 2 Ni 1.5 Sc 0.5 and Ni 2 Mn 1.5 Sc 0.5 are proposed as candidates for magnetic shape memory alloys. In these alloys, the Sc atom prefers occupying the D (0.75, 0.75, 0.75) sites in the Heusler alloy lattice and forms d–d hybridization with its nearest neighbor atoms such as Ni. Martensitic transformation is possible in both Mn 2 Ni 1.5 Sc 0.5 and Ni 2 Mn 1.5 Sc 0.5. Differing from the "volume-conserving" character in classic Heusler alloys, a large volume shrinkage of 2.3% and 2.8% occurs in Mn 2 Ni 1.5 Sc 0.5 and Ni 2 Mn 1.5 Sc 0.5 during the martensitic transformation, respectively. The magnetization difference between the austenite and martensite is as large as 4.50 μ B /f.u. for Mn 2 Ni 1.5 Sc 0.5 and 4.49 μ B /f.u. for Ni 2 Mn 1.5 Sc 0.5 , due to the ferromagnetic–antiferromagnetic magnetic transition coupling with the martensitic transformation. The parallel coupled Mn (B) and Mn (D) spin moments in the austenite become antiparallel in the martensite, which leads to the large decrease of magnetization after the martensitic transformation. The energy difference ΔE M between the martensite and austenite is −45.5 and −25.9 meV/f.u. for Mn 2 Ni 1.5 Sc 0.5 and Ni 2 Mn 1.5 Sc 0.5 , respectively. The large ΔE M of Mn 2 Ni 1.5 Sc 0.5 derives from the strong Jahn–Teller effect in its density of states structure and makes it a promising candidate for magnetic shape memory alloys. • New possible all-d-metal MSMAs Mn 2 Ni 1.5 Sc 0.5 and Ni 2 Mn 1.5 Sc 0.5 basing on Sc element have been proposed • Large volume effect is observed during the martensitic transformation in Mn 2 Ni 1.5 Sc 0.5 and Ni 2 Mn 1.5 Sc 0.5 • Mn 2 Ni 1.5 Sc 0.5 can be a promising MSMA with metamagnetic martensitic phase transition and large volume change [ABSTRACT FROM AUTHOR]

Transition metal Zn shows a main group element-like behavior in Heusler alloys Ni 2 MnGa 1−x Zn x (x = 0, 0.25, 0.50, 075 and 1.00). Zn enters Ga (D) site when it substitutes for Ga in Ni 2 MnGa chemically. The equilibrium lattice constant decreases with increasing Zn content. But at the same time the magnetic properties do not change too much. Mn partial moment contributes most to the total moment and couples parallel to that of Ni in both austenite and martensite. The partly substitution of Zn for Ga can lead to an increase of martensitic transition temperature due to the competition between cell volume effect and valence electron concentration e/a. Accordingly, the largest energy difference ΔE M between the austenite and martensite was found when x = 0.5. This was further explained based on the electronic structure from the Jahn-Teller effect. Then Zn-doping can be used as a possible way to adjust the phase transition temperatures in Heusler type MSMAs. Zn is much cheaper than Ga or In, this can be quite meaningful for the development of high performance and low cost MSMAs and broaden their industrial applications. [ABSTRACT FROM AUTHOR]

Influence of Fe substitution for Ni on the magnetic properties and martensitic transformation was investigated theoretically in Heusler alloys Ni 2 Mn 1.5 Z 0.5 (Z = In, Sb). Fe-doping does not change the general magnetic structure of Ni 2 Mn 1.5 Z 0.5 . In both Ni 2 Mn 15 In 0.5 and Ni 1.75 Fe 0.25 Mn 1.5 In 0.5 the austenitic phase is ferromagnetic and martensitic phase is antiferromagnetic, which leads to the large ΔM observed experimentally. But in Ni 2 Mn 1.5 Sb 0.5 and Ni 1.75 Fe 0.25 Mn 1.5 Sb 0.5 , the antiferromagnetic state is stable in both austenite and martensite. This difference is mainly related to the different atomic radii of In and Sb, which change the distance between Mn (B) and Mn (D). Parallel or antiparallel coupled Mn moments determine the magnetic properties of these alloys. But the partial moment of Fe is large and its direction reverses after martensitic transformation, which makes it a possible way to adjust the magnetic properties of MSMAs. Calculation also suggests that the substitution of Fe for Ni can lower the martensitic transition driving force and lead to the decrease of phase transition temperature. These results agree well with preceding experimental results and make reasonable explanation for them. [ABSTRACT FROM AUTHOR]

BCC Heusler phase Ni 2 CoSi has been predicted to be a promising candidate to realize magnetic field induced martensitic transformation. We tried to prepare Ni 2 CoSi single phase using different methods. Single phase Ni 2 CoSi cannot be synthesized by arc-melting and annealing. Then we used mechanical alloying method to synthesize Ni 2 CoSi. But a FCC phase rather than BCC was obtained after ball-milling. The lattice constant of FCC Ni 2 CoSi is 3.52 Å and the Curie temperature is around 900 K. The saturation magnetization at 5 K is 2.44μ B /f.u. This FCC phase is stable and no transition is observed when heating to 1173 K. The electronic structure and phase stability of the FCC and BCC Heusler phase have been investigated by first-principles calculations. The FCC Ni 2 CoSi has lower total energy compared with BCC, agreeing with the experimental observation. But the calculated total moment is much smaller than the M s at 5 K. This difference is related to the atomic disorder and was discussed by KKR-CPA calculation. [ABSTRACT FROM AUTHOR]

Heusler alloy Co 2 RuSi has been synthesized by melt-spinning technology successfully. Co 2 RuSi bulk sample after annealing is composed of an HCP Co-rich phase and a BCC Ru-Si phase, but melt-spinning can suppress the precipitation of the HCP phase and produce a single Co 2 RuSi Heusler phase. In the XRD pattern, it is found that Ru has a strong preference for the (A, C) sites, though it has fewer valence electrons compared with Co. This site preference is different from the case in Heusler alloys containing only 3d elements and is supported further by first-principles calculations. Melt-spun Co 2 RuSi has a M s of 2.67 μ B /f.u. at 5 K and a Tc of 491 K. An exothermic peak is observed at 871 K in the DTA curve, corresponding to the decomposition of the Heusler phase. Finally, the site preference and magnetic properties of Co 2 RuSi were discussed based on electronic structure calculation and charge density difference. [ABSTRACT FROM AUTHOR]

The site preference of 4d transition metal element Zr in Heusler alloys Zr 2 YAl (Y = Cr, Mn, Fe, Co, Ni) has been investigated theoretically. In these alloys the two Zr atoms prefer entering the A (0, 0, 0) and C (0.5, 0.5, 0.5) sites in the lattice of Heusler alloys and forming L2 1 structure (Cu 2 MnAl-type). This is different from previous predictions based on “number of valence electrons”, in which Zr atoms were predicted to occupy A (0, 0, 0) and B (0.25, 0.25, 0.25) sites and form XA (Hg 2 CuTi-type) structure. Present work suggests that L2 1 structure has a much lower total energy compared with XA type. Half-metallicity and spin gapless semiconductor character have been predicted in XA type Zr 2 YAl, but these properties may be disturbed under the more stable L2 1 structure. The energy difference between the XA and L2 1 structures increases as Y atom varies from Cr to Ni. The reason has been discussed based on the charge density difference. The magnetic properties of Zr 2 YAl have been investigated, a new possible Slater-Pauling curve of M = Z−22 has been observed in Zr 2 CoAl and Zr 2 NiAl. [ABSTRACT FROM AUTHOR]

The damping capacity of Ni 55−x Cu x Mn 25 Ga 20 (x = 0, 2, 4, 6) shape memory alloys is studied in details. The results show an increasing damping peak capacity with increasing Cu content. Especially, a high damping peak with the peak value of 0.08 is found in Ni 49 Cu 6 Mn 25 Ga 20 alloy, which spans over a wide temperature range of 173 K–425 K. The first-principles calculations indicate the substitution of Cu for Ni weakens the p-d orbital hybridization of Ni 55−x Cu x Mn 25 Ga 20 and reduces its martensite modulus, which thus enhances its twin boundary mobility and the damping capability. Our study sheds light on developing ambient-temperature high damping alloys. [ABSTRACT FROM AUTHOR]

• Melt-spinning can help to reduce precipitation of the secondary phase and form a highly ordered structure in Heusler alloys Fe 2 CoSi 1-x B x (x = 0–0.25) • B atoms mainly enter the substitutional site in Fe 2 CoSi 1-x B x and single Heusler phase can be obtained when × = 0–0.10. • Fe 2 CoSi 1-x B x Heusler alloys are candidates for spintronic applications within the range of × = 0–0.1. • Deviation between the M s at 5 K and calculated total spin moment is observed when B content is high, resulting from the Fe 2 B-type secondary phase. A series of Fe 2 CoSi 1-x B x (x = 0, 0.05, 0.1, 0.15, 0.2 and 0.25) Heusler alloys has been synthesized using melt-spinning method, which can help to reduce the precipitation of the secondary phase and form a highly ordered structure. The XRD patterns indicate that, when x = 0–0.1 the Fe 2 CoSi 1-x B x melt-spun ribbons are single Heusler phases, but when x = 0.2 and 0.25 a small amount of secondary phase appears. The lattice constant decreases with increasing B content, suggesting that B mainly enters the substitutional sites of Si. The Curie temperatures T C of Fe 2 CoSi 1-x B x alloys are all higher than 1000 K, and a 21 K increase of T C is observed as x varies from 0 to 0.25. The hysteresis loops of Fe 2 CoSi 1-x B x alloys show soft magnetic character. Their saturation magnetizations M s at 5 K and 300 K are similar and close to 5μ B / f.u. The zero-gap half-metallic character reported for Fe 2 CoSi has been confirmed in present work. But with the substitution of B for Si, the Fermi level moves from the center in Fe 2 CoSi DOS to the left edge of the minority energy gap in Fe 2 CoSi 0.75 B 0.25 , which may disturb the half-metallic character when B content is high. When × = 0–0.1, the M s at 5 K of Fe 2 CoSi 1-x B x agree well with the calculated total spin moments, but when the B content is high, especially when x = 0.2 and 0.25, a deviation between the experimental and theoretical results is observed, which is related to the secondary phase in these samples. [ABSTRACT FROM AUTHOR]