First-Principles Study of Magnetism-Dependent Phonons Governed by Exchange Ligand Field

Tanaka, Tomonori; Gohda, Yoshihiro

doi:10.7566/jpsj.89.093705

Cited by 10 publications

(2 citation statements)

References 30 publications

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“…In this sense, the LMD state is more suitable than the ground state as a reference state to determine due to the overestimation [ 17 , 51 , 52 ]. To understand the prominent stabilization in the paramagnetic state due to phonons, a concept called the exchange ligand field can be useful [ 57 ]. Developments of theoretical methods for finite-temperature magnetism (both the indirect effect of magnetism-dependent phonons on magnetism and the direct effect of atomic displacements and magnetic states on ) and applications to magnetic compounds involved in permanent magnets should stimulate further progress providing feedbacks with each other.…”

Section: Finite-temperature Magnetism For Intergranular Phases In Nd-mentioning

confidence: 99%

First-principles determination of intergranular atomic arrangements and magnetic properties in rare-earth permanent magnets

Gohda

2021

Science and Technology of Advanced Materials

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Development of high-performance permanent magnets relies on both the main-phase compound with superior intrinsic magnetic properties and the microstructure effect for the prevention of magnetization reversal. In this article, the microstructure effect is discussed by focusing on the interface between the main phase and an intergranular phase and on the intergranular phase itself. First, surfaces of main-phase grains are considered, where a general trend in the surface termination and its origin are discussed. Next, microstructure interfaces in SmFe 12 -based magnets are discussed, where magnetic decoupling between SmFe 12 grains is found for the SmCu subphase. Finally, general insights into finite-temperature magnetism are discussed with emphasis on the feedback effect from magnetism-dependent phonons on magnetism, which is followed by explanations on atomic arrangements and magnetism of intergranular phases in Nd-Fe-B magnets. Both amorphous and candidate crystalline structures of Nd-Fe alloys are considered. The addition of Cu and Ga to Nd-Fe alloys is demonstrated to be effective in decreasing the Curie temperature of the intergranular phase.

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Section: Finite-temperature Magnetism For Intergranular Phases In Nd-mentioning

confidence: 99%

First-principles determination of intergranular atomic arrangements and magnetic properties in rare-earth permanent magnets

Gohda

2021

Science and Technology of Advanced Materials

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“…27) First-principles evaluations of phonon free energies have large computational costs for systems with disorders such as random alloys and paramagnetic configurations. 28,29) Furthermore, computations of free energies for a wide composition range have another potential difficulty, i.e. the lattice instability.…”

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Structures of Sm–Cu intermetallics with Fe as subphase candidates in SmFe₁₂-based permanent magnets studied by first-principles thermodynamics

Nishino

Gohda²

2023

Jpn. J. Appl. Phys.

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Since crystalline grain-boundary subphases are expected in SmFe12-based permanent magnets, stable crystal structures dependent on temperatures and compositions are examined by first-principles thermodynamics. The free-energy landscape of ternary Sm-Cu-Fe is constructed with self-consistent phonon theory to overcome the dynamical instability problem, where a barrier between binary B2 Sm-Cu and bcc Fe is found. Cu-rich B2 Sm-Cu is substantially stabilized by phonons as well as by the configurational entropy. Furthermore, Fe atoms in the Cu sublattice of B27 SmCu contribute to the relative phase stabilization. These results indicate the existence of B2-B27 two-phase equilibria expanding the stable composition region of nonmagnetic SmCu-based intermetallics.

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Ab Initio Modeling on The Thermodynamic and Temperature-Dependent Elastic Properties of Subsystems of The FCC FeNiCoCr Medium Entropy Alloys (MEAs)

Yang,

Wang,

Liu

et al. 2023

Acta Materialia

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First-Principles Study of Magnetism-Dependent Phonons Governed by Exchange Ligand Field

Cited by 10 publications

References 30 publications

First-principles determination of intergranular atomic arrangements and magnetic properties in rare-earth permanent magnets

First-principles determination of intergranular atomic arrangements and magnetic properties in rare-earth permanent magnets

Structures of Sm–Cu intermetallics with Fe as subphase candidates in SmFe₁₂-based permanent magnets studied by first-principles thermodynamics

Ab Initio Modeling on The Thermodynamic and Temperature-Dependent Elastic Properties of Subsystems of The FCC FeNiCoCr Medium Entropy Alloys (MEAs)

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First-Principles Study of Magnetism-Dependent Phonons Governed by Exchange Ligand Field

Cited by 10 publications

References 30 publications

First-principles determination of intergranular atomic arrangements and magnetic properties in rare-earth permanent magnets

First-principles determination of intergranular atomic arrangements and magnetic properties in rare-earth permanent magnets

Structures of Sm–Cu intermetallics with Fe as subphase candidates in SmFe12-based permanent magnets studied by first-principles thermodynamics

Ab Initio Modeling on The Thermodynamic and Temperature-Dependent Elastic Properties of Subsystems of The FCC FeNiCoCr Medium Entropy Alloys (MEAs)

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Structures of Sm–Cu intermetallics with Fe as subphase candidates in SmFe₁₂-based permanent magnets studied by first-principles thermodynamics