Relationship between Magnetocrystalline Anisotropy and Orbital Magnetic Moment in<i>L</i>1<sub>0</sub>-Type Ordered and Disordered Alloys

Kota, Yohei; Sakuma, Atsushi

doi:10.1143/jpsj.81.084705

Cited by 79 publications

(80 citation statements)

References 30 publications

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“…The magnetic anisotropy constant ( K u ) of L 1 0 -FeNi is strongly correlated with the long-range order parameter, S , which is defined as follows:where p Fe is the Fe occupancy at the Fe site. In order to use L 1 0 -FeNi as a permanent magnet, the formation of high- S L 1 0 -FeNi is essential 13 so that the magnetic anisotropy of L 1 0 -FeNi is maximized. Furthermore, it is essential to derive single-phase L 1 0 -FeNi as bulk or bulkable powder.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

Goto¹,

Kura²,

Watanabe³

et al. 2017

Sci Rep

104

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Tetrataenite (L10-FeNi) is a promising candidate for use as a permanent magnet free of rare-earth elements because of its favorable properties. In this study, single-phase L10-FeNi powder with a high degree of order was synthesized through a new method, nitrogen insertion and topotactic extraction (NITE). In the method, FeNiN, which has the same ordered arrangement as L10-FeNi, is formed by nitriding A1-FeNi powder with ammonia gas. Subsequently, FeNiN is denitrided by topotactic reaction to derive single-phase L10-FeNi with an order parameter of 0.71. The transformation of disordered-phase FeNi into the L10 phase increased the coercive force from 14.5 kA/m to 142 kA/m. The proposed method not only significantly accelerates the development of magnets using L10-FeNi but also offers a new synthesis route to obtain ordered alloys in non-equilibrium states.

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Section: Introductionmentioning

confidence: 99%

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

Goto¹,

Kura²,

Watanabe³

et al. 2017

Sci Rep

104

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“…Furthermore, it is well-accepted that PMA is proportional to the anisotropy of the orbital magnetic moments, as predicted by Bruno27. However, considering that the large spin-orbit interaction in Pt 5 d states affects the PMA in the Co layer, the details of how to apply this formula are still being debated2829303132, and the relationship between orbital magnetic moments and PMA is not completely understood. Therefore, a better understanding of the orbital moment anisotropy in the Co/Pt interface and its modulation by Cu insertion is required in order to implement novel material designs possessing PMA.…”

mentioning

confidence: 99%

Induced perpendicular magnetization in a Cu layer inserted between Co and Pt layers revealed by x-ray magnetic circular dichroism

Okabayashi

Koyama

Suzuki

et al. 2017

Sci Rep

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We used x-ray absorption spectroscopy and x-ray magnetic circular dichroism to investigate the effects of inserting Cu into Co/Pt interfaces, and found that a 0.4-nm-thick inserted Cu layer showed perpendicularly magnetized properties induced by the proximity effect through the Co and Pt layers. The dependence of the magnetic properties on the thickness of the Cu layers showed that the proximity effects between Co and Pt with perpendicular magnetic anisotropy can be prevented by the insertion of a Cu layer with a nominal threshold thickness of 0.7 nm. Element-specific magnetization curves were also obtained, demonstrating that the out-of-plane magnetization is induced in the Cu layers of the Co/Cu/Pt structures.

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“…MAE in L1 0 compounds and tetragonal FeCo had been well studied 2,3,[15][16][17][18] . The calculated MAE values are in reasonable agreement with previous calculations 2, 3 .…”

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confidence: 99%

Constituents of magnetic anisotropy and a screening of spin–orbit coupling in solids

Antropov

Åberg

2014

Solid State Communications

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Using quantum mechanical perturbation theory (PT) we analyze how the energy of perturbation of different orders is renormalized in solids. We test the validity of PT analysis by considering a specific case of spin-orbit coupling as a perturbation. We further compare the relativistic energy and the magnetic anisotropy from the PT approach with direct density functional calculations in FePt, CoPt, FePd, MnAl, MnGa, FeNi, and tetragonally strained FeCo. In addition using decomposition of anisotropy into contributions from individual sites and different spin components we explain the microscopic origin of high anisotropy in FePt and CoPt magnets. The magnetocrystalline anisotropy is a central magnetic property for both fundamental and practical reasons.1-3 It can depend sensitively on many quantities such as dopants or small changes in lattice constant.4 While control of this sensitive quantity can be crucial in many applications, e.g. permanent magnetism 5 , magnetooptics 6 and magnetoresistive random-access memory devices 7 , it is often unclear what mechanisms are responsible for these anisotropy variations, even from a fundamental point of view. It was understood long ago 8,9 that the magnetic anisotropy energy (MAE) K in bulk materials is a result of simultaneous action of spin-orbit coupling (SOC) and crystal field (CF). While in general this statement is still valid, existing microscopic methods do not accurately describe K in the majority of materials. One can calculate MAE using ab-initio electronic structure methods based on density functional theory, however quantitative agreement is often rather poor. In any case such methods are usually not well equipped to resolve it into components that yield an intuitive understanding, to enable its manipulation and control. Sometimes K is analyzed in terms of SOC matrix elements of ξl·s, where ξ is the SOC constant. However, this perturbation also induces changes in other terms contributing the total energy, which can affect the MAE as well. Below we show how the actual atomic SOC is 'screened' in crystals and study spin decomposition of SOC and MAE in real world magnets.Let us write the total Hamiltonian of magnetic electronic system aswhere H 0 is the non-relativistic Hamiltonian (sum of kinetic and potential energies of electrons) and V = ξl·s is * Materials of this paper have been presented at the 58th Annual the SOC Hamiltonian. We assume that ξ is small relative to CF and spin splittings. The change in the total energy of the system when SOC is added (below we call it relativistic part of the total energy) can be written aswhere E so is the matrix element of SOC with full perturbed wavefunction and ∆E 0 is the induced energy change of the scalar-relativistic Hamiltonian ( sum of kinetic and potential energies) due to the SOC perturbation. Using standard quantum mechanical perturbation theory (PT) each quantity |φ = |n , E = E (n) and E so = V (n) (wave function, total energy and perturbation V ) can be expressed as a sum over orders n: V (n) is proportional to...

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Relationship between Magnetocrystalline Anisotropy and Orbital Magnetic Moment inL1₀-Type Ordered and Disordered Alloys

Cited by 79 publications

References 30 publications

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

Induced perpendicular magnetization in a Cu layer inserted between Co and Pt layers revealed by x-ray magnetic circular dichroism

Constituents of magnetic anisotropy and a screening of spin–orbit coupling in solids

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Relationship between Magnetocrystalline Anisotropy and Orbital Magnetic Moment inL10-Type Ordered and Disordered Alloys

Cited by 79 publications

References 30 publications

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

Induced perpendicular magnetization in a Cu layer inserted between Co and Pt layers revealed by x-ray magnetic circular dichroism

Constituents of magnetic anisotropy and a screening of spin–orbit coupling in solids

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Relationship between Magnetocrystalline Anisotropy and Orbital Magnetic Moment inL1₀-Type Ordered and Disordered Alloys