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Johanna Rosen - One of the best experts on this subject based on the ideXlab platform.
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theoretical prediction and synthesis of a family of atomic laminate metal borides with in plane Chemical Ordering
Journal of the American Chemical Society, 2020Co-Authors: Martin Dahlqvist, Quanzheng Tao, Justinas Palisaitis, Per Persson, Jie Zhou, Johanna RosenAbstract:All atomically laminated MAB phases (M = transition metal, A = A-group element, and B = boron) exhibit orthorhombic or tetragonal symmetry, with the only exception being hexagonal Ti2InB2. Inspired by the recent discovery of Chemically Ordered hexagonal carbides, i-MAX phases, we perform an extensive first-principles study to explore Chemical Ordering upon metal alloying of M2AlB2 (M from groups 3 to 9) in orthorhombic and hexagonal symmetry. Fifteen stable novel phases with in-plane Chemical Ordering are identified, coined i-MAB, along with 16 disOrdered stable alloys. The predictions are verified through the powder synthesis of Mo4/3Y2/3AlB2 and Mo4/3Sc2/3AlB2 of space group R3m (no. 166), displaying the characteristic in-plane Chemical Order of Mo and Y/Sc and Kagome Ordering of the Al atoms, as evident from X-ray diffraction and electron microscopy. The discovery of i-MAB phases expands the elemental space of these borides with M = Sc, Y, Zr, Hf, and Nb, realizing an increased property tuning potential of these phases as well as their suggested potential two-dimensional derivatives.
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predictive theoretical screening of phase stability for Chemical Order and disOrder in quaternary 312 and 413 max phases
Nanoscale, 2020Co-Authors: Martin Dahlqvist, Johanna RosenAbstract:In this work we systematically explore a class of atomically laminated materials, Mn+1AXn (MAX) phases upon alloying between two transition metals, M′ and M′′, from groups III to VI (Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W). The materials investigated focus on so called o-MAX phases with out-of-plane Chemical Ordering of M′ and M′′, and their disOrdered counterparts, for A = Al and X = C. Through use of predictive phase stability calculations, we confirm all experimentally known phases to date, and also suggest a range of stable Ordered and disOrdered hypothetical elemental combinations. Ordered o-MAX is favoured when (i) M′ next to the Al-layer does not form a corresponding binary rock-salt MC structure, (ii) the size difference between M′ and M′′ is small, and (iii) the difference in electronegativity between M′ and Al is large. Preference for Chemical disOrder is favoured when the size and electronegativity of M′ and M′′ is similar, in combination with a minor difference in electronegativity of M′ and Al. We also propose guidelines to use in the search for novel o-MAX; to combine M′ from group 6 (Cr, Mo, W) with M′′ from groups 3 to 5 (Sc only for 312, Ti, Zr, Hf, V, Nb, Ta). Correspondingly, we suggest formation of disOrdered MAX phases by combing M′ and M′′ within groups 3 to 5 (Sc, Ti, Zr, Hf, V, Nb, Ta). The addition of novel elemental combinations in MAX phases, and in turn in their potential two-dimensional MXene derivatives, allow for property tuning of functional materials.
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theoretical prediction and experimental verification of the Chemically Ordered atomic laminate i max phases cr2 3sc1 3 2gac and mn2 3sc1 3 2gac
Crystal Growth & Design, 2019Co-Authors: Andrejs Petruhins, Martin Dahlqvist, Lars Hultman, Jun Lu, Johanna RosenAbstract:We combine predictive ab-initio calculations with experimental verification of bulk materials synthesis for exploration of new and potentially magnetic atomically laminated i-MAX phases. Two such phases are discovered: (Cr2/3Sc1/3)2GaC and (Mn2/3Sc1/3)2GaC, where the latter compound displays a two-fold increase in Mn content compared to previously reported bulk MAX phases. Both new compounds exhibit the characteristic in-plane Chemical Order of Cr(Mn) and Sc, and crystallize in an orthorhombic structure, space group Cmcm, as confirmed by scanning transmission electron microscopy (STEM). From density functional theory (DFT) calculations of the magnetic ground state, including the electron-interaction parameter U, we suggest an antiferromagnetic ground state, close to degenerate with the ferromagnetic state.
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origin of Chemically Ordered atomic laminates i max expanding the elemental space by a theoretical experimental approach
ACS Nano, 2018Co-Authors: Martin Dahlqvist, Andrejs Petruhins, Lars Hultman, Johanna RosenAbstract:With increased Chemical diversity and structural complexity comes the opportunities for innovative materials possessing advantageous properties. Herein, we combine predictive first-principles calculations with experimental synthesis, to explore the origin of formation of the atomically laminated i-MAX phases. By probing (Mo2/3M1/32)2AC (where M2 = Sc, Y and A = Al, Ga, In, Si, Ge, In), we predict seven stable i-MAX phases, five of which should have a retained stability at high temperatures. (Mo2/3Sc1/3)2GaC and (Mo2/3Y1/3)2GaC were experimentally verified, displaying the characteristic in-plane Chemical Order of Mo and Sc/Y and Kagome-like Ordering of the A-element. We suggest that the formation of i-MAX phases requires a significantly different size of the two metals, and a preferable smaller size of the A-element. Furthermore, the population of antibonding orbitals should be minimized, which for the metals herein (Mo and Sc/Y) means that A-elements from Group 13 (Al, Ga, In) are favored over Group 14 (S...
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theoretical and experimental exploration of a novel in plane Chemically Ordered cr2 3m1 3 2alc i max phase with m sc and y
Crystal Growth & Design, 2017Co-Authors: Jun Lu, Andreas Thore, Rahele Meshkian, Lars Hultman, Johanna RosenAbstract:We have uncovered two inherently laminated transition metal carbides, (Cr2/3Sc1/3)2AlC and (Cr2/3Y1/3)2AlC, which display in-plane Chemical Order in carbide sheet and Kagome pattern in Al layer. The phases belong to the most recently discovered family of so called i-MAX phases. The materials were synthesized and the crystal structures evaluated by means of analytical high resolution scanning transmission electron microscopy, selected area electron diffraction, and X-ray diffraction Rietveld refinement. An orthorhombic structure of space group Cmcm (#63) and a monoclinic structure of space group C2/c (#15) are solved. The compounds were investigated by first principles calculations based on density functional theory, suggesting close to degenerate antiferro- and ferromagnetic spin states, dynamical and mechanical stability, and a Voigt bulk modulus in the range 134-152 GPa.
Martin Dahlqvist - One of the best experts on this subject based on the ideXlab platform.
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theoretical prediction and synthesis of a family of atomic laminate metal borides with in plane Chemical Ordering
Journal of the American Chemical Society, 2020Co-Authors: Martin Dahlqvist, Quanzheng Tao, Justinas Palisaitis, Per Persson, Jie Zhou, Johanna RosenAbstract:All atomically laminated MAB phases (M = transition metal, A = A-group element, and B = boron) exhibit orthorhombic or tetragonal symmetry, with the only exception being hexagonal Ti2InB2. Inspired by the recent discovery of Chemically Ordered hexagonal carbides, i-MAX phases, we perform an extensive first-principles study to explore Chemical Ordering upon metal alloying of M2AlB2 (M from groups 3 to 9) in orthorhombic and hexagonal symmetry. Fifteen stable novel phases with in-plane Chemical Ordering are identified, coined i-MAB, along with 16 disOrdered stable alloys. The predictions are verified through the powder synthesis of Mo4/3Y2/3AlB2 and Mo4/3Sc2/3AlB2 of space group R3m (no. 166), displaying the characteristic in-plane Chemical Order of Mo and Y/Sc and Kagome Ordering of the Al atoms, as evident from X-ray diffraction and electron microscopy. The discovery of i-MAB phases expands the elemental space of these borides with M = Sc, Y, Zr, Hf, and Nb, realizing an increased property tuning potential of these phases as well as their suggested potential two-dimensional derivatives.
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predictive theoretical screening of phase stability for Chemical Order and disOrder in quaternary 312 and 413 max phases
Nanoscale, 2020Co-Authors: Martin Dahlqvist, Johanna RosenAbstract:In this work we systematically explore a class of atomically laminated materials, Mn+1AXn (MAX) phases upon alloying between two transition metals, M′ and M′′, from groups III to VI (Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W). The materials investigated focus on so called o-MAX phases with out-of-plane Chemical Ordering of M′ and M′′, and their disOrdered counterparts, for A = Al and X = C. Through use of predictive phase stability calculations, we confirm all experimentally known phases to date, and also suggest a range of stable Ordered and disOrdered hypothetical elemental combinations. Ordered o-MAX is favoured when (i) M′ next to the Al-layer does not form a corresponding binary rock-salt MC structure, (ii) the size difference between M′ and M′′ is small, and (iii) the difference in electronegativity between M′ and Al is large. Preference for Chemical disOrder is favoured when the size and electronegativity of M′ and M′′ is similar, in combination with a minor difference in electronegativity of M′ and Al. We also propose guidelines to use in the search for novel o-MAX; to combine M′ from group 6 (Cr, Mo, W) with M′′ from groups 3 to 5 (Sc only for 312, Ti, Zr, Hf, V, Nb, Ta). Correspondingly, we suggest formation of disOrdered MAX phases by combing M′ and M′′ within groups 3 to 5 (Sc, Ti, Zr, Hf, V, Nb, Ta). The addition of novel elemental combinations in MAX phases, and in turn in their potential two-dimensional MXene derivatives, allow for property tuning of functional materials.
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theoretical prediction and experimental verification of the Chemically Ordered atomic laminate i max phases cr2 3sc1 3 2gac and mn2 3sc1 3 2gac
Crystal Growth & Design, 2019Co-Authors: Andrejs Petruhins, Martin Dahlqvist, Lars Hultman, Jun Lu, Johanna RosenAbstract:We combine predictive ab-initio calculations with experimental verification of bulk materials synthesis for exploration of new and potentially magnetic atomically laminated i-MAX phases. Two such phases are discovered: (Cr2/3Sc1/3)2GaC and (Mn2/3Sc1/3)2GaC, where the latter compound displays a two-fold increase in Mn content compared to previously reported bulk MAX phases. Both new compounds exhibit the characteristic in-plane Chemical Order of Cr(Mn) and Sc, and crystallize in an orthorhombic structure, space group Cmcm, as confirmed by scanning transmission electron microscopy (STEM). From density functional theory (DFT) calculations of the magnetic ground state, including the electron-interaction parameter U, we suggest an antiferromagnetic ground state, close to degenerate with the ferromagnetic state.
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origin of Chemically Ordered atomic laminates i max expanding the elemental space by a theoretical experimental approach
ACS Nano, 2018Co-Authors: Martin Dahlqvist, Andrejs Petruhins, Lars Hultman, Johanna RosenAbstract:With increased Chemical diversity and structural complexity comes the opportunities for innovative materials possessing advantageous properties. Herein, we combine predictive first-principles calculations with experimental synthesis, to explore the origin of formation of the atomically laminated i-MAX phases. By probing (Mo2/3M1/32)2AC (where M2 = Sc, Y and A = Al, Ga, In, Si, Ge, In), we predict seven stable i-MAX phases, five of which should have a retained stability at high temperatures. (Mo2/3Sc1/3)2GaC and (Mo2/3Y1/3)2GaC were experimentally verified, displaying the characteristic in-plane Chemical Order of Mo and Sc/Y and Kagome-like Ordering of the A-element. We suggest that the formation of i-MAX phases requires a significantly different size of the two metals, and a preferable smaller size of the A-element. Furthermore, the population of antibonding orbitals should be minimized, which for the metals herein (Mo and Sc/Y) means that A-elements from Group 13 (Al, Ga, In) are favored over Group 14 (S...
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theoretical prediction and synthesis of cr2 3zr1 3 2alc i max phase
Inorganic Chemistry, 2018Co-Authors: Liugang Chen, Martin Dahlqvist, Rahele Meshkian, Jun Lu, Thomas Lapauw, Bensu Tunca, Fei Wang, Konstantina Lambrinou, Bart Blanpain, Jozef VleugelsAbstract:Guided by predictive theory, a new compound with Chemical composition (Cr2/3Zr1/3)2AlC was synthesized by hot pressing of Cr, ZrH2, Al, and C mixtures at 1300 °C. The crystal structure is monoclinic of space group C2/c and displays in-plane Chemical Order in the metal layers, a so-called i-MAX phase. Quantitative Chemical composition analyses confirmed that the primary phase had a (Cr2/3Zr1/3)2AlC stoichiometry, with secondary Cr2AlC, AlZrC2, and ZrC phases and a small amount of Al–Cr intermetallics. A theoretical evaluation of the (Cr2/3Zr1/3)2AlC magnetic structure was performed, indicating an antiferromagnetic ground state. Also (Cr2/3Hf1/3)2AlC, of the same structure, was predicted to be stable.
Jun Lu - One of the best experts on this subject based on the ideXlab platform.
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theoretical prediction and experimental verification of the Chemically Ordered atomic laminate i max phases cr2 3sc1 3 2gac and mn2 3sc1 3 2gac
Crystal Growth & Design, 2019Co-Authors: Andrejs Petruhins, Martin Dahlqvist, Lars Hultman, Jun Lu, Johanna RosenAbstract:We combine predictive ab-initio calculations with experimental verification of bulk materials synthesis for exploration of new and potentially magnetic atomically laminated i-MAX phases. Two such phases are discovered: (Cr2/3Sc1/3)2GaC and (Mn2/3Sc1/3)2GaC, where the latter compound displays a two-fold increase in Mn content compared to previously reported bulk MAX phases. Both new compounds exhibit the characteristic in-plane Chemical Order of Cr(Mn) and Sc, and crystallize in an orthorhombic structure, space group Cmcm, as confirmed by scanning transmission electron microscopy (STEM). From density functional theory (DFT) calculations of the magnetic ground state, including the electron-interaction parameter U, we suggest an antiferromagnetic ground state, close to degenerate with the ferromagnetic state.
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theoretical prediction and synthesis of cr2 3zr1 3 2alc i max phase
Inorganic Chemistry, 2018Co-Authors: Liugang Chen, Martin Dahlqvist, Rahele Meshkian, Jun Lu, Thomas Lapauw, Bensu Tunca, Fei Wang, Konstantina Lambrinou, Bart Blanpain, Jozef VleugelsAbstract:Guided by predictive theory, a new compound with Chemical composition (Cr2/3Zr1/3)2AlC was synthesized by hot pressing of Cr, ZrH2, Al, and C mixtures at 1300 °C. The crystal structure is monoclinic of space group C2/c and displays in-plane Chemical Order in the metal layers, a so-called i-MAX phase. Quantitative Chemical composition analyses confirmed that the primary phase had a (Cr2/3Zr1/3)2AlC stoichiometry, with secondary Cr2AlC, AlZrC2, and ZrC phases and a small amount of Al–Cr intermetallics. A theoretical evaluation of the (Cr2/3Zr1/3)2AlC magnetic structure was performed, indicating an antiferromagnetic ground state. Also (Cr2/3Hf1/3)2AlC, of the same structure, was predicted to be stable.
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theoretical and experimental exploration of a novel in plane Chemically Ordered cr2 3m1 3 2alc i max phase with m sc and y
Crystal Growth & Design, 2017Co-Authors: Jun Lu, Andreas Thore, Rahele Meshkian, Lars Hultman, Johanna RosenAbstract:We have uncovered two inherently laminated transition metal carbides, (Cr2/3Sc1/3)2AlC and (Cr2/3Y1/3)2AlC, which display in-plane Chemical Order in carbide sheet and Kagome pattern in Al layer. The phases belong to the most recently discovered family of so called i-MAX phases. The materials were synthesized and the crystal structures evaluated by means of analytical high resolution scanning transmission electron microscopy, selected area electron diffraction, and X-ray diffraction Rietveld refinement. An orthorhombic structure of space group Cmcm (#63) and a monoclinic structure of space group C2/c (#15) are solved. The compounds were investigated by first principles calculations based on density functional theory, suggesting close to degenerate antiferro- and ferromagnetic spin states, dynamical and mechanical stability, and a Voigt bulk modulus in the range 134-152 GPa.
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Theoretical stability and materials synthesis of a Chemically Ordered MAX phase, Mo2ScAlC2, and its two-dimensional derivate Mo2ScC2 MXene
Acta Materialia, 2017Co-Authors: Rahele Meshkian, Quanzheng Tao, Martin Dahlqvist, Lars Hultman, Jun Lu, Johanna RosenAbstract:We present theoretical prediction and experimental evidence of a new MAX phase alloy, Mo2ScAlC2, with out-of-plane Chemical Order. Evaluation of phase stability was performed by ab initio calculations based on Density Functional Theory, suggesting that Chemical Order in the alloy promotes a stable phase, with a formation enthalpy of −24 meV/atom, as opposed to the predicted unstable Mo3AlC2 and Sc3AlC2. Bulk synthesis of Mo2ScAlC2 is achieved by mixing elemental powders of Mo, Sc, Al and graphite which are heated to 1700 °C. High resolution transmission electron microscopy reveals a Chemically Ordered structure consistent with theoretical predictions with one Sc layer sandwiched between two Mo[sbnd]C layers. The two-dimensional derivative, the MXene, is produced by selective etching of the Al-layers in hydrofluoric acid, resulting in the corresponding Chemically Ordered Mo2ScC2, i.e. the first Sc-containing MXene. The here presented results expands the attainable range of MXene compositions and widens the prospects for property tuning.
Lars Hultman - One of the best experts on this subject based on the ideXlab platform.
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theoretical prediction and experimental verification of the Chemically Ordered atomic laminate i max phases cr2 3sc1 3 2gac and mn2 3sc1 3 2gac
Crystal Growth & Design, 2019Co-Authors: Andrejs Petruhins, Martin Dahlqvist, Lars Hultman, Jun Lu, Johanna RosenAbstract:We combine predictive ab-initio calculations with experimental verification of bulk materials synthesis for exploration of new and potentially magnetic atomically laminated i-MAX phases. Two such phases are discovered: (Cr2/3Sc1/3)2GaC and (Mn2/3Sc1/3)2GaC, where the latter compound displays a two-fold increase in Mn content compared to previously reported bulk MAX phases. Both new compounds exhibit the characteristic in-plane Chemical Order of Cr(Mn) and Sc, and crystallize in an orthorhombic structure, space group Cmcm, as confirmed by scanning transmission electron microscopy (STEM). From density functional theory (DFT) calculations of the magnetic ground state, including the electron-interaction parameter U, we suggest an antiferromagnetic ground state, close to degenerate with the ferromagnetic state.
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origin of Chemically Ordered atomic laminates i max expanding the elemental space by a theoretical experimental approach
ACS Nano, 2018Co-Authors: Martin Dahlqvist, Andrejs Petruhins, Lars Hultman, Johanna RosenAbstract:With increased Chemical diversity and structural complexity comes the opportunities for innovative materials possessing advantageous properties. Herein, we combine predictive first-principles calculations with experimental synthesis, to explore the origin of formation of the atomically laminated i-MAX phases. By probing (Mo2/3M1/32)2AC (where M2 = Sc, Y and A = Al, Ga, In, Si, Ge, In), we predict seven stable i-MAX phases, five of which should have a retained stability at high temperatures. (Mo2/3Sc1/3)2GaC and (Mo2/3Y1/3)2GaC were experimentally verified, displaying the characteristic in-plane Chemical Order of Mo and Sc/Y and Kagome-like Ordering of the A-element. We suggest that the formation of i-MAX phases requires a significantly different size of the two metals, and a preferable smaller size of the A-element. Furthermore, the population of antibonding orbitals should be minimized, which for the metals herein (Mo and Sc/Y) means that A-elements from Group 13 (Al, Ga, In) are favored over Group 14 (S...
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theoretical and experimental exploration of a novel in plane Chemically Ordered cr2 3m1 3 2alc i max phase with m sc and y
Crystal Growth & Design, 2017Co-Authors: Jun Lu, Andreas Thore, Rahele Meshkian, Lars Hultman, Johanna RosenAbstract:We have uncovered two inherently laminated transition metal carbides, (Cr2/3Sc1/3)2AlC and (Cr2/3Y1/3)2AlC, which display in-plane Chemical Order in carbide sheet and Kagome pattern in Al layer. The phases belong to the most recently discovered family of so called i-MAX phases. The materials were synthesized and the crystal structures evaluated by means of analytical high resolution scanning transmission electron microscopy, selected area electron diffraction, and X-ray diffraction Rietveld refinement. An orthorhombic structure of space group Cmcm (#63) and a monoclinic structure of space group C2/c (#15) are solved. The compounds were investigated by first principles calculations based on density functional theory, suggesting close to degenerate antiferro- and ferromagnetic spin states, dynamical and mechanical stability, and a Voigt bulk modulus in the range 134-152 GPa.
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Theoretical stability and materials synthesis of a Chemically Ordered MAX phase, Mo2ScAlC2, and its two-dimensional derivate Mo2ScC2 MXene
Acta Materialia, 2017Co-Authors: Rahele Meshkian, Quanzheng Tao, Martin Dahlqvist, Lars Hultman, Jun Lu, Johanna RosenAbstract:We present theoretical prediction and experimental evidence of a new MAX phase alloy, Mo2ScAlC2, with out-of-plane Chemical Order. Evaluation of phase stability was performed by ab initio calculations based on Density Functional Theory, suggesting that Chemical Order in the alloy promotes a stable phase, with a formation enthalpy of −24 meV/atom, as opposed to the predicted unstable Mo3AlC2 and Sc3AlC2. Bulk synthesis of Mo2ScAlC2 is achieved by mixing elemental powders of Mo, Sc, Al and graphite which are heated to 1700 °C. High resolution transmission electron microscopy reveals a Chemically Ordered structure consistent with theoretical predictions with one Sc layer sandwiched between two Mo[sbnd]C layers. The two-dimensional derivative, the MXene, is produced by selective etching of the Al-layers in hydrofluoric acid, resulting in the corresponding Chemically Ordered Mo2ScC2, i.e. the first Sc-containing MXene. The here presented results expands the attainable range of MXene compositions and widens the prospects for property tuning.
M Richard - One of the best experts on this subject based on the ideXlab platform.
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magnetic moment and Chemical Order in off stoichiometric ni mn ga ferromagnetic shape memory alloys
New Journal of Physics, 2011Co-Authors: P Lazpita, J M Barandiaran, J Gutierrez, J Feuchtwanger, V A Chernenko, M RichardAbstract:Recent studies have shown that the total magnetic moment in off-stoichiometric Ni–Mn–Ga alloys depends not only on electronic concentration but also on the degree of Chemical Order in the alloy. We have performed neutron diffraction experiments and magnetization measurements for determining the preferential atomic Order and saturation moment in off-stoichiometric compounds (44–52 at.% Ni), having excess Mn and deficient in Ga. These alloys include isoelectronic alloys with different magnetic moments and were chosen in an effort to study the impact of Chemical Order on the magnetic moment distribution. In this work, we present an improved model of magnetic interaction between Mn atoms, which carry most of the localized magnetic moment of the alloys. The Mn atoms at Ga sites, which are nearest neighbors to properly sited Mn, couple antiferromagnetically to the dominant moment. In contrast, Mn atoms at Ga sites, which are nearest neighbors to Mn at Ni sites, couple ferromagnetically. Mn at Ni sites is always antiferromagnetic (AF). The new model is supported by the exchange variation with the Mn–Mn distance and demonstrates excellent agreement between experimental and calculated magnetic moments. The proposed model is shown to better explain the observed experimental results as compared to the rigid band model and previous localized moment models that assumed AF coupling for all off-site Mn atoms.
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Chemical Order in off stoichiometric ni mn ga ferromagnetic shape memory alloys studied with neutron diffraction
Philosophical Magazine, 2007Co-Authors: M Richard, P Lazpita, J M Barandiaran, J Gutierrez, J Feuchtwanger, Samuel M Allen, Robert C Ohandley, B Ouladdiaf, C Mondelli, Thomas A LograssoAbstract:The Chemical Order of three off-stoichiometry Ni–Mn–Ga compositions has been measured in the austenitic phase using powder and single-crystal neutron diffraction. The compositions studied, 48–52 at.% nickel, having excess manganese and deficient in gallium, are of technical interest due to the observed large room-temperature, magnetic-field-induced strain. It has been determined that compositions with less than 50% nickel have the excess Mn atoms occupying Ni and Ga sites. Compositions enriched in nickel are best fit with Ni atoms in excess of 50% occupying Mn sites while the excess and displaced Mn occupy Ga sites. The saturation magnetic moments calculated from the site occupations determined here and using Ni and Mn moments reported for Ni2MnGa, agree within 4% with the low-temperature measured moments.
