Lattice symmetry of the spiral spin-density-wave state in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>γ</mml:mi><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Fe</mml:mi></mml:mrow></mml:math>precipitates in Cu

Tsunoda, Yorihiko; Nogami, Hajime; Takasaka, Masao

doi:10.1103/physrevb.76.054419

Cited by 8 publications

(10 citation statements)

References 20 publications

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“…28 Below the Néel temperature of ∼ 70 K (Refs. 29 and 30), it has been found in both experimental 31 and theoretical [32][33][34] studies that the magnetic ground state is strongly dependent on the lattice parameters, which, in turn, depend on the growth conditions. As a result, both an AFM state and a spin-spiral state have been reported.…”

Section: Introductionmentioning

confidence: 99%

Structural and magnetic ground-state properties ofγ-FeMn alloys fromab initiocalculations

Ekholm

Abrikosov

2011

Phys. Rev. B

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The magnetic properties of fcc-FeMn alloys, especially at the Fe 0.5 Mn 0.5 composition, have been the subject of intense experimental and theoretical investigations for several decades. We carry out an ab initio theoretical study of this system, including simultaneous optimization of structural and magnetic properties, and find that the ground state is the locally relaxed noncollinear 3Q antiferromagnetic structure. We also show that the two most frequently used parameterizations of the generalized gradient approximation not only fail to reproduce the equilibrium lattice constant of FeMn alloys, and consequently the magnetic properties, but also internally yield qualitatively different results. For practical studies of these alloys, which currently attract great attention, we propose a set of approximations, which is internally consistent, and brings the equilibrium lattice constant and magnetic properties in good agreement with the experiment in the whole range of alloy compositions.

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Section: Introductionmentioning

confidence: 99%

Structural and magnetic ground-state properties ofγ-FeMn alloys fromab initiocalculations

Ekholm

Abrikosov

2011

Phys. Rev. B

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“…There has been considerable experimental effort to stabilize γ -Fe at lower temperatures, primarily by epitaxial growth of thin films on Cu substrates (e.g., Meyerheim et al 1 ) and by the formation of γ -Fe precipitates by heat treatment of dilute alloys of Fe in fcc Cu (e.g., Tsunoda et al 2 and Hines et al 3 ). For a review of earlier work, see Marsman and Hafner.…”

Section: Introductionmentioning

confidence: 99%

Defect and solute properties in dilute Fe-Cr-Ni austenitic alloys from first principles

2012

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We present results of an extensive set of first-principles density functional theory calculations of point defect formation, binding, and clustering energies in austenitic Fe with dilute concentrations of Cr and Ni solutes. A large number of possible collinear magnetic structures were investigated as appropriate reference states for austenite. We found that the antiferromagnetic single-and double-layer structures with tetragonal relaxation of the unit cell were the most suitable reference states and highlighted the inherent instabilities in the ferromagnetic states. Test calculations for the presence and influence of noncollinear magnetism were performed but proved mostly negative. We calculate the vacancy formation energy to be between 1.8 and 1.95 eV. Vacancy cluster binding was initially weak at 0.1 eV for divacancies but rapidly increased with additional vacancies. Clusters of up to six vacancies were studied and a highly stable octahedral cluster and stacking fault tetrahedron were found with total binding energies of 2.5 and 2.3 eV, respectively. The 100 dumbbell was found to be the most stable self-interstitial with a formation energy of between 3.2 and 3.6 eV and was found to form strongly bound clusters, consistent with other fcc metals. Pair interaction models were found to be capable of capturing the trends in the defect cluster binding energy data. Solute-solute interactions were found to be weak in general, with a maximal positive binding of 0.1 eV found for Ni-Ni pairs and maximum repulsion found for Cr-Cr pairs of −0.1 eV. Solute cluster binding was found to be consistent with a pair interaction model, with Ni-rich clusters being the most stable. Solute-defect interactions were consistent with Ni and Cr being modestly oversized and undersized solutes, respectively, which is exactly opposite to the experimentally derived size factors for Ni and Cr solutes in type 316 stainless steel and in the pure materials. Ni was found to bind to the vacancy and to the 100 dumbbell in the tensile site by 0.1 eV and was repelled from mixed and compressive sites. In contrast, Cr showed a preferential binding to interstitials. Calculation of tracer diffusion coefficients found that Ni diffuses significantly more slowly than both Cr and Fe, which is consistent with the standard mechanism used to explain radiation-induced segregation effects in Fe-Cr-Ni austenitic alloys by vacancy-mediated diffusion. Comparison of our results with those for bcc Fe showed strong similarity for pure Fe and no correlation with dilute Ni and Cr.

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“…Thus, it is difficult to conduct experimental studies of defect and solute properties in dilute fcc Fe. Considerable experimental efforts have therefore been carried out to stabilize the γ -Fe at lower temperature [8][9][10] (Fe is fcc at 1185-1664 K) to improve the current level of understanding by studying the magnetic ordering. These experiments have shown that γ -Fe displays a noncollinear, spiral magnetic structure.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

Piochaud¹,

Klaver²,

Adjanor³

et al. 2014

Phys. Rev. B

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The influence of the local environment on vacancy and self-interstitial formation energies has been investigated in a face-centered-cubic (fcc) Fe-10Ni-20Cr model alloy by analyzing an extensive set of first-principle calculations based on density functional theory. Chemical disorder has been considered by designing special quasirandom structures and four different collinear magnetic structures have been investigated in order to determine a relevant reference state to perform point defect calculations at 0 K. Two different convergence methods have also been used to characterize the importance of the method on the results. Although our fcc Fe-10Ni-20Cr would be better represented in terms of applications by the paramagnetic state, we found that the antiferromagnetic single-layer magnetic structure was the most stable at 0 K and we chose it as a reference state to determine the point defect properties. Point defects have been introduced in this reference state, i.e., vacancies and Fe-Fe, Fe-Ni, Fe-Cr, Cr-Cr, Ni-Ni, and Ni-Cr dumbbell interstitials oriented either parallel or perpendicular to the single layer antiferromagnetic planes. Each point defect studied was introduced at different lattice sites to consider a sufficient variety of local environments and analyze its influence on the formation energy values. We have estimated the point defect formation energies with linear regressions using variables which describe the local environment surrounding the point defects. The number and the position of Ni and Cr first nearest neighbors to the point defects were found to drive the evolution of the formation energies. In particular, Ni is found to decrease and Cr to increase the vacancy formation energy of the model alloy, while the opposite trends are found for the dumbbell interstitials. This study suggested that, to a first approximation, the first nearest atoms to point defects can provide reliable estimates of point defect formation energies.

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Lattice symmetry of the spiral spin-density-wave state inγ−Feprecipitates in Cu

Cited by 8 publications

References 20 publications

Structural and magnetic ground-state properties ofγ-FeMn alloys fromab initiocalculations

Structural and magnetic ground-state properties ofγ-FeMn alloys fromab initiocalculations

Defect and solute properties in dilute Fe-Cr-Ni austenitic alloys from first principles

First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

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