Enhanced spin–orbit coupling in tetragonally strained Fe–Co–B films

Salikhov, Ruslan; Reichel, Ludwig; Zingsem, Benjamin; Abrudan, R.; Edström, Alexander; Thonig, Danny; Rusz, Ján; Eriksson, Olle; Schultz, L.; Fähler, Sebastian; Farle, Michael; Wiedwald, Ulf

doi:10.1088/1361-648x/aa7498

Cited by 16 publications

(12 citation statements)

References 70 publications

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“…[2][3][4][5][6][7] Some of the promising candidates studied recently are e.g. Fe/Co nanowires 8,9 , Fe-Co alloys doped with B and C [10][11][12][13] , (Fe/Co) 2 B [14][15][16][17] , (Fe/Co) 5 XB 2 [18][19][20] , MnBi 21 , and the L1 0 phases such as FePt, CoNi, MnAl, and FeNi. [22][23][24] The last candidate on the list is a subject of this work.…”

Section: Introductionmentioning

confidence: 99%

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Werwiński¹,

Marciniak²

2017

J. Phys. D: Appl. Phys.

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The ordered L1 0 FeNi phase (tetrataenite) is recently considered as a promising candidate for the rare-earth free permanent magnets applications. In this work we calculate several characteristics of the L1 0 FeNi, where most of the results come form the fully relativistic full potential FPLO method with the generalized gradient approximation (GGA). A special attention deserves the summary of the magnetocrystalline anisotropy energies (MAE's), the full potential calculations of the anisotropy constant K 3 , and the combined analysis of the Fermi surface and three-dimensional k-resolved MAE. Other calculated parameters presented in this article are the magnetic moments ms and m l , magnetostrictive coefficient λ 001 , bulk modulus B 0 , and lattice parameters. The MAE's summary shows rather big discrepancies between the experimental MAE's from literature and also between the calculated MAE's. The MAE's calculated in this work with the full potential and GGA are equal to 0.47 MJ m −3 from WIEN2k, 0.34 MJ m −3 from FPLO, and 0.23 MJ m −3 from FP-SPR-KKR code. These last results strongly suggest that the value of MAE in GGA is below 0.5 MJ m −3 . It is also expected that this value is significantly underestimated due to the limitations of the GGA. Unfortunately, as other authors suggest, even the MAE equal 1.3 MJ m −3 would be insufficient to raise the L1 0 FeNi from the category of semi-hard magnets. However the L1 0 FeNi has still a potential to improve its MAE by modifications, like e.g. tetragonal strain or alloying. The presented three-dimensional k-resolved map of the MAE combined with the Fermi surface gives a complete picture of the MAE contributions in the Brillouin zone. The calculated Fermi surface consists of closed hole pockets and open sheets. It reflects a four-fold symmetry of the crystal and is closely related to the MAE(k). The analysis of the effects of external factors, like strain, on the k-resolved MAE and Fermi surface should be beneficial in engineering of the hard magnetic properties. The obtained from full potential FP-SPR-KKR method magnetocrystalline anisotropy constants K 2 and K 3 are several orders of magnitude smaller than the MAE/K 1 and equal to -2.0 kJ m −3 and 110 J m −3 , respectively. The calculated partial spin and orbital magnetic moments of the L1 0 FeNi are equal to 2.72 and 0.054 µ B for Fe and 0.53 and 0.039 µ B for Ni atoms, respectively. The calculations of geometry optimization lead to a c/a ratio equal to 1.0036, B 0 equal to 194 GPa, and λ 001 equal to 9.4 × 10 −6 .

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Section: Introductionmentioning

confidence: 99%

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Werwiński¹,

Marciniak²

2017

J. Phys. D: Appl. Phys.

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“…An interesting question is how such tetragonal distortions can be stabilized. We suspect that light interstitial atoms such as H, B, C, and N will lead to substantial tetragonal distortions, as recently investigated in Fe [61] and FeCo [62,63] alloys. Systematic calculations have been performed on compounds with the Cu 3 Au (as for Mn 3 Pt) and Heusler (as for Mn 2 RhPt and Fe 2 CoGa) structures with light interstitials, and the results will be reported elsewhere.…”

Section: Tetragonally Distortion Of Cubic Phasesmentioning

confidence: 79%

“…Finally, concerning the cubic phases in which a tetragonal distortion can induce a large MAE (see Section 4.2.2), we think that adding light interstitial atoms such as H, B, C, and N in these compounds might be a likely way to achieve it in practice [61,62,63]. Figure 18: Strategy to make use of Novamag database for tuning Fe 3 Sn phase.…”

Section: Possible Strategies To Exploit Promising Theoretical Novel Pmentioning

confidence: 99%

Database of novel magnetic materials for high-performance permanent magnet development

Nieves

Arapan

Maudes

et al. 2019

Computational Materials Science

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This paper describes the open Novamag database that has been developed for the design of novel Rare-Earth free/lean permanent magnets. The database software technologies, its friendly graphical user interface, advanced search tools and available data are explained in detail. Following the philosophy and standards of Materials Genome Initiative, it contains significant results of novel magnetic phases with high magnetocrystalline anisotropy obtained by three computational high-throughput screening approaches based on a crystal structure prediction method using an Adaptive Genetic Algorithm, tetragonally distortion of cubic phases and tuning known phases by doping. Additionally, it also includes theoretical and experimental data about fundamental magnetic material properties such as magnetic moments, magnetocrystalline anisotropy energy, exchange parameters, Curie temperature, domain wall width, exchange stiffness, coercivity and maximum energy product, that can be used in the study and design of new promising high-performance Rare-Earth free/lean permanent magnets. The results therein contained might provide some insights into the ongoing debate about the theoretical performance limits beyond Rare-Earth based magnets. Finally, some general strategies are discussed to design possible experimental routes for exploring most promising theoretical novel materials found in the database. NOVAMAG H c > M r /2 [5]. Extrinsic properties also depend on temperature, in fact they typically decrease as temperature increases, reducing the magnet's performance, especially close to the Curie temperature T C (i.e. ferromagnetic-paramagenetic transition). The macroscopic behavior is tightly linked to the microscopic properties called intrinsic. Main magnetic intrinsic properties are atomic magnetic moment µ at (the magnetic moment per volume gives the maximum theoretical M s ), exchange interactions J ij (which determine the magnetic order and T C )and magnetocrystalline anisotropy K 1 (that can enhance H c and it is indispensable in modern magnets to get H c > M r /2) [6]. PMs should have high atomic mangetic moments per volume (> 0.1µ B /Å 3 ), strong ferromangetic exchange interactions (able to give T C > 600 K) and high easy axis magnetocrystalline anisotropy (K 1 > 1 MJ/m 3 ) in order to exhibit good extrinsic properties suitable for PM applcations. In particular, magnetic materials with hardness parameter κ = K 1 /(µ 0 M 2 s ) > 1 (called "hard" magnets) are very valuable since can be used to make efficient magnets of any shape [6]. At mesoscopic scale, intergranular structure between the grains and crystallographic defects can strongly affect the performance of a magnet [7]. Therefore, the optimization of the material's microstructure is also very important in the design and devel-

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“…7 ). All the spectra show resonances at magnetic fields smaller than ω / γ = 336 mT ( ω = 2π ν , ν is the microwave frequency, γ = gμ B /ħ is the electron gyromagnetic ratio, g = 2.1 is the spectroscopic splitting factor assumed for the Fe 50 Ni 50 39 ), thus indicating that the magnetization easy axis preferentially lies in the film plane due to the larger contribution of magnetic shape anisotropy in FeNi films 40 , 41 . The in-plane angular dependent measurements do not reveal any magnetic anisotropy with axial symmetry lying in the film plane.…”

Section: Resultsmentioning

confidence: 99%

“…In any case, the obtained MCA energy densities in all the samples are by two orders of magnitude larger than the values known for the cubic Fe 50 Ni 50 alloy 44 . The film thickness of 40 nm is large enough to exclude a significant interface contribution to the MCA 29 , 40 . WAXS and HR-STEM analyses reveal the presence of the ordered L1 0 -FeNi phase, which explains the relatively large MCA in all the samples.…”

Section: Resultsmentioning

confidence: 99%

L10-FeNi films on Au-Cu-Ni buffer-layer: a high-throughput combinatorial study

Giannopoulos

Barucca

Kaidatzis

et al. 2018

Sci Rep

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The fct L10-FeNi alloy is a promising candidate for the development of high performance critical-elements-free magnetic materials. Among the different materials, the Au-Cu-Ni alloy has resulted very promising; however, a detailed investigation of the effect of the buffer-layer composition on the formation of the hard FeNi phase is still missing. To accelerate the search of the best Au-Cu-Ni composition, a combinatorial approach based on High-Throughput (HT) experimental methods has been exploited in this paper. HT magnetic characterization methods revealed the presence of a hard magnetic phase with an out-of-plane easy-axis, whose coercivity increases from 0.49 kOe up to 1.30 kOe as the Au content of the Cu-Au-Ni buffer-layer decreases. Similarly, the out-of-plane magneto-crystalline anisotropy energy density increases from 0.12 to 0.35 MJ/m3. This anisotropy is attributed to the partial formation of the L10 FeNi phase induced by the buffer-layer. In the range of compositions we investigated, the buffer-layer structure does not change significantly and the modulation of the magnetic properties with the Au content in the combinatorial layer is mainly related to the different nature and extent of interlayer diffusion processes, which have a great impact on the formation and order degree of the L10 FeNi phase.

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Enhanced spin–orbit coupling in tetragonally strained Fe–Co–B films

Cited by 16 publications

References 70 publications

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Database of novel magnetic materials for high-performance permanent magnet development

L10-FeNi films on Au-Cu-Ni buffer-layer: a high-throughput combinatorial study

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Enhanced spin–orbit coupling in tetragonally strained Fe–Co–B films

Cited by 16 publications

References 70 publications

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L10FeNi (tetrataenite)

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L10FeNi (tetrataenite)

Database of novel magnetic materials for high-performance permanent magnet development

L10-FeNi films on Au-Cu-Ni buffer-layer: a high-throughput combinatorial study

Contact Info

Product

Resources

About

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)

Ab initiostudy of magnetocrystalline anisotropy, magnetostriction, and Fermi surface of L1₀FeNi (tetrataenite)