Dynamics of magnetism in Fe-Cr alloys with Cr clustering

Chapman, Jacob B. J.; Ma, Pui-Wai; Dudarev, S. L.

doi:10.1103/physrevb.99.184413

Cited by 23 publications

(17 citation statements)

References 75 publications

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“…As expected from the ASRO inversion, chosen concentration range, and heat treatment, we do not observe segregation in any of the studied alloys. For 0.2 < x < 0.4, such segregation can be detected by neutron small angle scattering [61,62], atom probe tomography [51], and its kinetics simulated by atomistic Monte Carlo [63] and dynamic [64] simulations. In the nuclear cross section, it would appear as an intensity peak in the range 0.1 K 0.4 Å −1 related to the typical distance between precipitates [65].…”

Section: Neutron Resultsmentioning

confidence: 99%

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Magnetic and atomic short range order in Fe1−xCrx alloys

et al. 2019

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We study the magnetic short range order (MSRO) in Fe 1−x Cr x (0 x 0.15) where an inversion of atomic short range order (ASRO) occurs at x C = 0.11(1). Our combination of neutron diffuse scattering and bulk magnetization measurements offers a comprehensive description of these local orders at a microscopic level. In the dilute alloys (x < 0.04), the Cr atoms bear a large moment μ Cr = −1.0(1) μ B , antiparallel to the Fe ones (μ Fe ). They fully repel their Cr first and second neighbors, and perturb the surrounding Fe moments. With increasing x, near neighbor Cr-Cr pairs start to appear and the Cr moment magnitude decreases, while μ Fe shows a rounded maximum for x 1 = 0.06(1) < x C . Above x C , ASRO turns to local Cr segregation, thereby increasing magnetic frustration. First-principles calculations reproduce the observed moment variations but overestimate the magnitude of the Cr moment. In order to reconcile theory with experiment quantitatively, we propose that the magnetic moments start canting locally, already above x 1 . This picture actually anticipates the spin glasslike behavior of Cr-rich alloys. The whole study points out the subtle interplay of MSRO and ASRO, yielding an increasing frustration as x increases, due to competing Fe-Cr and Cr-Cr interactions and Cr clustering tendency.

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Section: Neutron Resultsmentioning

confidence: 99%

“…The spin canting and maximum of μ Fe at x 1 are linked with a maximum of the Curie temperature [64,67]. All features reflect the onset of magnetic frustration induced by the competition of FM Fe-Fe, AFM Cr-Cr, and Cr-Fe near neighbor interactions.…”

Section: A Dilute Impurity Limitmentioning

confidence: 86%

Magnetic and atomic short range order in Fe1−xCrx alloys

et al. 2019

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“…Recently, theoretical concepts of the decomposition of alloys that contain magnetic components have been further developed [13,[16][17][18][19] owing to the emergence of new experimental data and ab initio calculation results. The role of magnetism in the decomposition of Fe-Cr alloys was discussed in [16].…”

Section: Theory Of Metalsmentioning

confidence: 99%

“…The role of magnetism in the decomposition of Fe-Cr alloys was discussed in [16]. In [17,18], the use of the method of magnetic cluster decomposition made it possible to propose a consistent approach to the description of the thermodynamics and kinetics of the decomposition of Fe-Cr alloys. In [19], attention was drawn to the fact that the use of the ab initio mixing energies leads to significant overestimation of the decomposition temperature.…”

Section: Theory Of Metalsmentioning

confidence: 99%

Model of Decomposition of Alloy with Two Magnetic Components: the BCC FeCr System

Razumov

Gornostyrev

2021

Phys. Metals Metallogr.

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A sequential model of the decomposition of the bcc FeCr binary alloy is formulated that takes into account the configurational and magnetic contributions to the free energy. Using the results of ab initio calculations, the theory of regular solutions is generalized by considering the contributions of the magnetic entropy, the concentration dependence of the exchange interactions, and the mixing energies. The resulting expression for the free energy makes it possible to construct the boundaries of the two-phase region of the bcc FeCr alloy in good agreement with the experimental data, as well as to predict the position of the spinodal, below which the formation of highly dispersed states should be expected when starting from a homogeneous state.

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“…In this regard, frustration and spin canting should arise from the competition of ferromagnetic Fe-Fe, antiferromagnetic Cr-Cr (Mn-Mn), as well as antiferromagnetic Cr(Mn)-Fe nearest-neighbor exchange interactions, depending on the concentration [28,30]. This magnetic frustration is expected to reduce the saturation magnetization and lower the effective Curie temperature [30]. Schematics of various spin structures are illustrated in Fig.…”

Section: Introductionmentioning

confidence: 99%

L10 -ordered (Fe100−xCrx)Pt thin films: Pha

et al. 2020

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Chemically ordered L1 0 (Fe 100−x Cr x )Pt thin films were expitaxially grown on MgO(001) substrates by magnetron sputter-deposition at 770 • C. In this sample series, Fe was continuously substituted by Cr over the full composition range. The lattice parameter in the [001] growth direction steadily increases from L1 0 -FePt toward L1 0 -CrPt, confirming the incorporation of Cr in the lattice occupying Fe sites. With the observed high degree of chemical ordering and (001) orientation, strong perpendicular magnetic anisotropy is associated, which persists up to a Cr content of x = 20 at. %. Similarly, the coercive field in the easy-axis direction is strongly reduced, which is, however, further attributed to a strong alteration of the film morphology with Cr substitution. The latter changes from a well-separated island microstructure to a more continuous film morphology. In the dilute alloy with low Cr content, isolated Cr magnetic moments couple antiferromagnetically to the ferromagnetic Fe matrix. In this case, all Cr moments are aligned parallel, thus forming a ferrimagnetic FeCrPt system. With increasing Cr concentration, nearest-neighbor Cr-Cr pairs start to appear, thereby increasing magnetic frustration and disorder, which lead to canting of neighboring magnetic moments, as revealed by atomistic spin-model simulations with model parameters based on first principles. At higher Cr concentrations, a frustrated ferrimagnetic order is established. With Cr substitution of up to 20 at. %, no pronounced change in Curie temperature, which is in the range of 700 K, was noticed. But with further addition the Curie temperature drops down substantially even down to room temperature at 47 at. % Cr. Furthermore, x-ray magnetic circular dichroism studies on dilute alloys containing up to 20 at. % of Cr revealed similar spin moments for Fe and Cr in the range between 2.1-2.5 μ B but rather large orbital moments of up to 0.50 ±0.10 μ B for Cr. These results were also compared to ab initio calculations.

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Dynamics of magnetism in Fe-Cr alloys with Cr clustering

Cited by 23 publications

References 75 publications

Magnetic and atomic short range order in Fe1−xCrx alloys

Magnetic and atomic short range order in Fe1−xCrx alloys

Model of Decomposition of Alloy with Two Magnetic Components: the BCC FeCr System

L10 -ordered (Fe100−xCrx)Pt thin films: Pha

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