Structure and magnetic properties of highly ordered Co2NiGa alloys

Dai, Xuefang; Liu, Guodong; Li, Yangxian; Qu, Jinping; Li, Jia; Chen, Jinglan; Wu, Guangheng

doi:10.1063/1.2709417

Cited by 21 publications

(38 citation statements)

References 13 publications

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“…For the face-centered ␥ phase a Pt 2 FeCu-type ordering has been proposed previously. 43 From our calculations, however, it appears that this ordering is by 137 meV/f.u. higher in energy than the two considered Heusler arrangements and thus is not further considered, here.…”

Section: A Martensitic Transformations and Binding Surface In Stoichmentioning

confidence: 58%

Electronic structure and lattice dynamics of the magnetic shape-memory alloyCo2NiGa

et al. 2010

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In addition to the prototypical Ni-Mn-based Heusler alloys, the Co-Ni-Ga systems have recently been suggested as another prospective materials class for magnetic shape-memory applications. We provide a characterization of the dynamical properties of this material and their relation to the electronic structure within a combined experimental and theoretical approach. This relies on inelastic neutron scattering to obtain the phonon dispersion while first-principles calculations provide the link between dynamical properties and electronic structure. In contrast to Ni 2 MnGa, where the softening of the TA 2 phonon branch is related to Fermi-surface nesting, our results reveal that the respective anomalies are absent in Co-Ni-Ga, in the phonon dispersions as well as in the electronic structure. Keywords Materials Science and Engineering Disciplines Condensed Matter Physics | Materials Science and Engineering CommentsThis article is from Physical Review B 82 (2010) In addition to the prototypical Ni-Mn-based Heusler alloys, the Co-Ni-Ga systems have recently been suggested as another prospective materials class for magnetic shape-memory applications. We provide a characterization of the dynamical properties of this material and their relation to the electronic structure within a combined experimental and theoretical approach. This relies on inelastic neutron scattering to obtain the phonon dispersion while first-principles calculations provide the link between dynamical properties and electronic structure. In contrast to Ni 2 MnGa, where the softening of the TA 2 phonon branch is related to Fermisurface nesting, our results reveal that the respective anomalies are absent in Co-Ni-Ga, in the phonon dispersions as well as in the electronic structure.

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Section: A Martensitic Transformations and Binding Surface In Stoichmentioning

confidence: 58%

Electronic structure and lattice dynamics of the magnetic shape-memory alloyCo2NiGa

et al. 2010

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“…This structure can actually be visualized as two interpenetrating bcc lattices with B2-type ordering, in which the majority atom (A) occupies the body-centered sites and the other minority atoms (B and C) occupy alternate corners. Contrary to what is observed in most Heusler-type FSMAs, the austenite phase in Co-Ni-Ga alloys has a stoichiometry close to Co 2 NiGa but seems to have B2-type ordering (β phase) as opposed to L2 1 , although there is no definite conclusion in this regard 9,10 .…”

mentioning

confidence: 80%

“…Ordered and disordered alloys of Co 2 NiGa have also been studied experimentally 9 . Comparison of the magnetic properties of ordered and disordered phases suggest that ordering can increase the magnetization by 40%.…”

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confidence: 99%

Effect of configurational order on the magnetic characteristics of Co-Ni-Ga ferromagnetic shape memory alloys

et al. 2011

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In most of the ternary (and higher order) ferromagnetic shape memory alloys (FSMAs) with compositions close to the A2BC stoichiometry, the austenite phase exhibits L21-type ordering. Recent investigations of the Co-Ni-Ga FSMA system, however, suggest that the austenite phase has B2-type ordering, although definite confirmation remains elusive. In this work, we present a theoretical investigation of the effect of configurational order on the magnetic properties of ordered (L21) and disordered (B2) FSMA Co2NiGa. Through the use of calculations based on density functional theory, we predict the structural and magnetic properties (including magnetic exchange constants) of ordered and disordered Co2NiGa alloys. We validate our calculation of the magnetic exchange constants by extracting the Curie temperatures of the austenite and martensite structures and comparing them to experiments. By constructing a q-state Potts magnetic Hamiltonian and through the use of lattice Monte Carlo simulation, we predict the finite temperature behavior of the magnetization, magnetic susceptibility as well as the magnetic specific heat and entropy. The role of configurational order on the magnetic properties of the phases involved in the martensitic phase transformation is discussed and predictions of the magnitude of the magnetic contributions to the transformation entropy are presented.The calculations are compared to experimental information available in the literature as well as experiments performed by the authors. It is concluded that in FSMAs, magnetism plays a fundamental role in determining the relative stability of the austenite and martensite phases, which in turn determines the martensitic transformation temperature MS, irrespective of whether magnetic fields are used to drive the transformation.

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“…The Curie temperatures of the austenite, T [35]) and a unit cell parameter of a = 2.8752(1) Å. As a minor phase with a content of 5.5(1.1) wt%, a fully-ordered γ phase with a slightly tetragonally distorted structure (P/4mmm, sg: 123, ICSD Code 157788 [34]) and unit cell parameters of a = 3.580(3) Å and c = 3.567(5) Å is detected (Table 1). In the β Co 2 NiGa structure with B2-type ordering, the Ni and Ga atoms occupy the same position, whereas in the tetragonal γ-phase, different atoms are placed in different positions [34,35] and the unit cell volume is approximately two-times larger than that of the β phase.…”

Section: Magnetic Propertiesmentioning

confidence: 99%

“…Concomitantly, the Curie temperature of the austenite T In addition to these well-investigated Ni-and Mn-based compounds, other FSMAs have been studied, i.e., Ni-Fe-Ga [21][22][23], Co-Ni-Al [24,25] and Co-Ni-Ga [26][27][28][29]. The Co-Ni-Ga Heusler system was intensively studied as a promising alternative to Ni-Mn-Ga alloys, especially for high-temperature shape memory device applications [30][31][32][33][34][35][36][37]. Co-Ni-Ga compounds generally exhibit a dual-phase microstructure: a parent phase (β) and a non-transformable secondary phase (γ).…”

Section: Introductionmentioning

confidence: 99%

Effects of Annealing on the Martensitic Transformation of Ni-Based Ferromagnetic Shape Memory Heusler Alloys and Nanoparticles

Fichtner

Wang

Levin

et al. 2015

Metals

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We report on the effects of annealing on the martensitic phase transformation in the Ni-based Heusler system: Mn 50 Ni 40 Sn 10 and Mn 50 Ni 41 Sn 9 powder and Co 50 Ni 21 Ga 32 nanoparticles. For the powdered Mn 50 Ni 40 Sn 10 and Mn 50 Ni 41 Sn 9 alloys, structural and magnetic measurements reveal that post-annealing decreases the martensitic transformation temperatures and increases the transition hysteresis. This might be associated with a release of stress in the Mn 50 Ni 40 Sn 10 and Mn 50 Ni 41 Sn 9 alloys during the annealing process. However, in the case of Co 50 Ni 21 Ga 32 nanoparticles, a reverse phenomenon is observed. X-ray diffraction analysis results reveal that the as-prepared Co 50 Ni 21 Ga 32 nanoparticles do not show a martensitic phase at room temperature. Post-annealing followed by ice quenching, however, is found to trigger the formation of the martensitic phase. The presence of the martensitic transition is attributed to annealing-induced particle growth and the stress introduced during quenching.

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Structure and magnetic properties of highly ordered Co2NiGa alloys

Cited by 21 publications

References 13 publications

Electronic structure and lattice dynamics of the magnetic shape-memory alloyCo2NiGa

Electronic structure and lattice dynamics of the magnetic shape-memory alloyCo2NiGa

Effect of configurational order on the magnetic characteristics of Co-Ni-Ga ferromagnetic shape memory alloys

Effects of Annealing on the Martensitic Transformation of Ni-Based Ferromagnetic Shape Memory Heusler Alloys and Nanoparticles

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