TY - JOUR

T1 - Plane wave implementation of the magnetic force theorem for magnetic exchange constants

T2 - application to bulk Fe, Co and Ni

AU - Durhuus, Frederik L.

AU - Skovhus, Thorbjørn

AU - Olsen, Thomas

N1 - Publisher Copyright:
© 2023 IOP Publishing Ltd.

PY - 2023

Y1 - 2023

N2 - We present a plane wave implementation of the magnetic force theorem, which provides a first principles framework for extracting exchange constants parameterizing a classical Heisenberg model description of magnetic materials. It is shown that the full microscopic exchange tensor may be expressed in terms of the static Kohn-Sham susceptibility tensor and the exchange-correlation magnetic field. This formulation allows one to define arbitrary magnetic sites localized to predefined spatial regions, hence rendering the problem of finding Heisenberg parameters independent of any orbital decomposition of the problem. The susceptibility is calculated in a plane wave basis, which allows for systematic convergence with respect to unoccupied bands and spatial representation. We then apply the method to the well-studied problem of calculating adiabatic spin wave spectra for bulk Fe, Co and Ni, finding good agreement with previous calculations. In particular, we utilize the freedom of defining magnetic sites to show that the calculated Heisenberg parameters are robust towards changes in the definition of magnetic sites. This demonstrates that the magnetic sites can be regarded as well-defined and thus asserts the relevance of the Heisenberg model description despite the itinerant nature of the magnetic state.

AB - We present a plane wave implementation of the magnetic force theorem, which provides a first principles framework for extracting exchange constants parameterizing a classical Heisenberg model description of magnetic materials. It is shown that the full microscopic exchange tensor may be expressed in terms of the static Kohn-Sham susceptibility tensor and the exchange-correlation magnetic field. This formulation allows one to define arbitrary magnetic sites localized to predefined spatial regions, hence rendering the problem of finding Heisenberg parameters independent of any orbital decomposition of the problem. The susceptibility is calculated in a plane wave basis, which allows for systematic convergence with respect to unoccupied bands and spatial representation. We then apply the method to the well-studied problem of calculating adiabatic spin wave spectra for bulk Fe, Co and Ni, finding good agreement with previous calculations. In particular, we utilize the freedom of defining magnetic sites to show that the calculated Heisenberg parameters are robust towards changes in the definition of magnetic sites. This demonstrates that the magnetic sites can be regarded as well-defined and thus asserts the relevance of the Heisenberg model description despite the itinerant nature of the magnetic state.

KW - DFT

KW - Exchange

KW - Magnetic excitations

KW - Magnetic force theorem

KW - Spin-waves

U2 - 10.1088/1361-648X/acab4b

DO - 10.1088/1361-648X/acab4b

M3 - Journal article

C2 - 36595249

AN - SCOPUS:85145641505

SN - 0953-8984

VL - 35

JO - Journal of Physics Condensed Matter

JF - Journal of Physics Condensed Matter

IS - 10

M1 - 105802

ER -