Origin of magnetocrystalline anisotropy in Ni-Mn-Ga-Co-Cu tetragonal martensite

Zelený, Michal; Straka, Ladislav; Rameš, Michal; Sozinov, A.; Heczko, Oleg

doi:10.1016/j.jmmm.2020.166522

Cited by 13 publications

(9 citation statements)

References 53 publications

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“…One should keep in mind that within the GGA+U method, increasing U on Mn sites results in a stronger SIC for the 3d-Mn orbitals. Several authors [60][61][62] have shown that the parameter U is needed to obtain better agreement with experiments for elastic constants, tetragonal ratios, and magnetic anisotropy energy of Ni 2 MnGa. In particular, Refs.…”

Section: B Reduction Of Sicmentioning

confidence: 99%

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Electronic structure beyond the generalized gradient approximation for Ni2MnGa

et al. 2020

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The stability of the nonmodulated martensitic phase, the austenitic Fermi surface and the phonon dispersion relations for ferromagnetic Ni2MnGa are studied using density functional theory. Exchange-correlation effects are considered with various degrees of precision, starting from the simplest local spin density approximation (LSDA), then adding corrections within the generalized gradient approximation (GGA) and finally, including the meta-GGA corrections within the strongly constrained and appropriately normed (SCAN). We discuss a simple procedure to reduce a possible overestimation of magnetization and underestimation of nesting vector in SCAN by parametrically decreasing self-interaction corrections.

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Section: B Reduction Of Sicmentioning

confidence: 99%

“…In particular, Refs. 61,62 have shown that U should be 1.8 eV for Mn. This value is smaller than the effective Coulomb correlation of 2 eV in SCAN, therefore in order to improve the agreement with experiment, one needs to consider a revised SCAN scheme where the SIC is reduced at the Mn sites.…”

Section: B Reduction Of Sicmentioning

confidence: 99%

Electronic structure beyond the generalized gradient approximation for Ni2MnGa

et al. 2020

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“…The reported U values used on the Mn d orbitals range from U = 5.97 eV calculated by the linear response approach 43 to U = 3.93 eV obtained by a fit to the experimental elastic constants 44 . Even a lower value of U = 1.8 eV was applied to Mn in works on doped Ni–Mn–Ga alloys in order to fit experiments on martensite phases 45 , 46 . The calculations with U on Mn larger than 1.2 eV correctly identify the five-layered modulated martensite (10M) as the ground state structure 47 while GGA predicts a theoretical four-layered 4O martensite as the most stable structure 48 .…”

Section: Introductionmentioning

confidence: 99%

Localization versus delocalization of d-states within the $$\hbox {Ni}_{{2}}$$MnGa Heusler alloy

Janovec

Zelený

Heczko

et al. 2022

Sci Rep

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We present calculations based on density-functional theory with improved exchange-correlation approaches to investigate the electronic structure of $$\hbox {Ni}_2$$ Ni 2 MnGa magnetic shape memory alloy prototype. We study the effects of hybrid functionals as well as a Hubbard-like correction parameter U on the structural, electronic and magnetic properties of the alloy. We show that the previously successful application of U on Mn should be extended by including U on Ni to describe the d localized electrons more accurately and in better agreement with experiments. The bonding interactions within this intermetallic alloy are analysed including the role of non-transition metal. We found that the strongest and most stabilizing bond is formed between the Ga–Ni pairs due to the delocalized s–s and p–s orbital hybridization. Our findings suggest that minimization of the over-delocalization error introduced by standard semi-local exchange-correlation functionals leads to a better description of the $$\hbox {Ni}_2$$ Ni 2 MnGa alloy. Furthermore we propose that the experimental total magnetic moment of Ni–Mn–Ga alloys could be increased after carefully selected heat treatment procedures.

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“…In addition, the DFT calculation correctly predicted the reduced

c / a

ratio, and, to a lesser extent, the MCA. [ 188 ] This example shows that, despite appearing to have the same crystal structure, NM martensites with additional alloyed elements have different stability with respect to twinning than Mn‐rich NM martensite and that the ab initio calculations may allow for a direct and reliable insight into this difference. Elastic stability with respect to twinning is an important parameter for MIR, and it will be discussed in the next section.…”

Section: Beyond a Perfect Lattice: Off‐stoichiometry Alloying And Ord...mentioning

confidence: 99%

Experimental Observations versus First‐Principles Calculations for Ni–Mn–Ga Ferromagnetic Shape Memory Alloys: A Review

Seiner

Zelený

Sedlák

et al. 2022

Physica Rapid Research Ltrs

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This review summarizes recent advances in first‐principles simulations of the structural, mechanical, and magnetomechanical properties of Ni–Mn–Ga‐based ferromagnetic shape memory alloys from the perspective of experimental characterization. It focuses on calculations that can capture the main features of the low‐temperature phases, particularly the appearance of spatial modulations, the occurrence of intermartensitic transitions, and the high mobility of the twin boundaries, which allows for magnetically induced reorientation. Although the calculations can only be used to interpret some of these features and are not yet ready to be used as a tool for designing new alloys with the required properties, the gap between experimental observations and simulations is narrowing. When experiments and theory are discussed together, new challenges arise for both. In addition, new results on first‐principles‐determined elastic constants of the 10M martensite of Ni–Mn–Ga are presented and discussed with respect to the high mobility of the twin boundaries.

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Origin of magnetocrystalline anisotropy in Ni-Mn-Ga-Co-Cu tetragonal martensite

Cited by 13 publications

References 53 publications

Electronic structure beyond the generalized gradient approximation for Ni2MnGa

Electronic structure beyond the generalized gradient approximation for Ni2MnGa

Localization versus delocalization of d-states within the $$\hbox {Ni}_{{2}}$$MnGa Heusler alloy

Experimental Observations versus First‐Principles Calculations for Ni–Mn–Ga Ferromagnetic Shape Memory Alloys: A Review

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