Ab initio study of the anomalous volume-composition dependence in Fe–Al alloys

Friák, Martin; Neugebauer, Jörg

doi:10.1016/j.intermet.2010.03.014

Cited by 38 publications

(38 citation statements)

References 28 publications

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“…The computed values of local magnetic moments of Fe atoms are plotted as functions of the number of Al atoms in the 1NN in Figure 2. The visualized trends show the local magnetic moments of Fe atoms decreasing with the increasing number of Al atoms in the 1NN of Fe atoms in a qualitative agreement with our previous studies [22,39]. Regarding the Al atoms in the 2NN shell, we did not find any clear impact-see Appendix A. APB-free B2 (see Fig.…”

Section: Resultssupporting

confidence: 90%

“…The computed magnitude of local magnetic moments in both APB-free B2 phase ( Figure 1b) and the APB-containing one ( Figure 1c) are visualized in Figure 1e,f, respectively, by spheres with different radius. As the local magnetic moments of Fe atoms in Fe-rich Fe-Al binaries decrease with an increasing number of Al atoms in the first nearest neighbors shell (1NN) of Fe atoms [22,39], we analyze these relations also here. The computed values of local magnetic moments of Fe atoms are plotted as functions of the number of Al atoms in the 1NN in Figure 2.…”

Section: Resultsmentioning

confidence: 99%

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An Ab Initio Study of Magnetism in Disordered Fe-Al Alloys with Thermal Antiphase Boundaries

et al. 2019

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We have performed a quantum-mechanical study of a B2 phase of Fe 70 Al 30 alloy with and without antiphase boundaries (APBs) with the {001} crystallographic orientation of APB interfaces. We used a supercell approach with the atoms distributed according to the special quasi-random structure (SQS) concept. Our study was motivated by experimental findings by Murakami et al. (Nature Comm. 5 (2014) 4133) who reported significantly higher magnetic flux density from A2-phase interlayers at the thermally-induced APBs in Fe 70 Al 30 and suggested that the ferromagnetism is stabilized by the disorder in the A2 phase. Our computational study of sharp APBs (without any A2-phase interlayer) indicates that they have moderate APB energies (≈0.1 J/m 2 ) and cannot explain the experimentally detected increase in the ferromagnetism because they often induce a ferro-to-ferrimagnetic transition. When studying thermal APBs, we introduce a few atomic layers of A2 phase of Fe 70 Al 30 into the interface of sharp APBs. The averaged computed magnetic moment of Fe atoms in the whole B2/A2 nanocomposite is then increased by 11.5% w.r.t. the B2 phase. The A2 phase itself (treated separately as a bulk) has the total magnetic moment even higher, by 17.5%, and this increase also applies if the A2 phase at APBs is sufficiently thick (the experimental value is 2–3 nm). We link the changes in the magnetism to the facts that (i) the Al atoms in the first nearest neighbor (1NN) shell of Fe atoms nonlinearly reduce their magnetic moments and (ii) there are on average less Al atoms in the 1NN shell of Fe atoms in the A2 phase. These effects synergically combine with the influence of APBs which provide local atomic configurations not existing in an APB-free bulk. The identified mechanism of increasing the magnetic properties by introducing APBs with disordered phases can be used as a designing principle when developing new magnetic materials.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

An Ab Initio Study of Magnetism in Disordered Fe-Al Alloys with Thermal Antiphase Boundaries

et al. 2019

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“…3b, we assume the alloy composition in the APB region to be Fe 72 Al 28 ; that is, a slight increase in Fe content occurs compared with the value in the matrix, Fe 70 Al 30 . According to a report by Friák and Neugebauer20, binary Fe–Al alloys show a dramatic increase in magnetization (with increasing Fe content) in the Fe content range between 65 and 70%. In contrast, magnetization increases gradually over the Fe composition range higher than 70%.…”

Section: Discussionmentioning

confidence: 99%

“…Phenomenologically, the amplified magnetization can be explained by the framework concerned with nearest Fe–Fe pairs, which are responsible for the ferromagnetic spin order1720222324. As factors affecting the number of nearest Fe–Fe pairs, we consider both atomic disordering and enrichment of the Fe content in the APB region.…”

Section: Discussionmentioning

confidence: 99%

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Magnetization amplified by structural disorder within nanometre-scale interface region

et al. 2014

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Direct magnetization measurements from narrow, complex-shaped antiphase boundaries (APBs; that is, planar defect produced in any ordered crystals) are vitally important for advances in materials science and engineering. However, in-depth examination of APBs has been hampered by the lack of experimental tools. Here, based on electron microscopy observations, we report the unusual relationship between APBs and ferromagnetic spin order in Fe70Al30. Thermally induced APBs show a finite width (2–3 nm), within which significant atomic disordering occurs. Electron holography studies revealed an unexpectedly large magnetic flux density at the APBs, amplified by approximately 60% (at 293 K) compared with the matrix value. At elevated temperatures, the specimens showed a peculiar spin texture wherein the ferromagnetic phase was confined within the APB region. These observations demonstrate ferromagnetism stabilized by structural disorder within APBs, which is in direct contrast to the traditional understanding. The results accordingly provide rich conceptual insights for engineering APB-induced phenomena.

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Casting of Iron Aluminides

Ramirez

Schön

2017

J. Phase Equilib. Diffus.

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Ab initio study of the anomalous volume-composition dependence in Fe–Al alloys

Cited by 38 publications

References 28 publications

An Ab Initio Study of Magnetism in Disordered Fe-Al Alloys with Thermal Antiphase Boundaries

An Ab Initio Study of Magnetism in Disordered Fe-Al Alloys with Thermal Antiphase Boundaries

Magnetization amplified by structural disorder within nanometre-scale interface region

Casting of Iron Aluminides

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