The effect of grain boundaries on magnetic exchange interactions in iron

Abstract

This work investigates how grain boundaries (GBs) modify magnetic exchange interactions in bcc iron, with particular focus on the effect of phosphorus segregation. Using density-functional theory combined with the Liechtenstein–Katsnelson–Antropov–Gubanov Green’s-function approach, we calculate Heisenberg exchange parameters for three symmetric tilt GBs, Σ5(310), Σ13(510), and Σ13(320), and use these parameters in Monte Carlo (MC) simulations to evaluate finite-temperature magnetic behavior. All clean GBs exhibit strong local deviations from bulk exchange interactions, including antiferromagnetic coupling across the boundary plane. These negative exchange interactions are not governed by interatomic distance alone, but arise primarily from the altered local coordination and symmetry breaking at the GB. Phosphorus segregation, modeled in both substitutional and interstitial configurations at the Σ5(310) GB, suppresses the antiferromagnetic couplings and significantly redistributes the local exchange landscape through chemical and electronic effects. MC results show that, despite pronounced local perturbations, realistic GB densities cause only a small reduction in the Curie temperature because bulk-like regions dominate the global magnetic transition. A substantial decrease in Curie temperature appears only when the GB volume fraction is artificially increased. The results demonstrate that GBs strongly influence local magnetic interactions while having a limited effect on global magnetic ordering, and they establish a general framework for linking atomistic interfacial structure and chemistry to mesoscale magnetic behavior in Fe-based materials.

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BibTeX RIS

BibTeX

@article{zeleny2026effect,
  title = {{The effect of grain boundaries on magnetic exchange interactions in iron}},
  author = {Martin Zelený and Martin Heczko and Petr Šesták and Denis Ledue and Renaud Patte and Miroslav Černý},
  journal = {Journal of Physics D: Applied Physics},
  year = {2026},
  month = jul,
  doi = {10.1088/1361-6463/ae84dc},
  eprint = {2604.10489},
  archivePrefix = {arXiv},
  url = {https://hal.science/hal-05775737v1},
  note = {CC BY},
}

RIS

TY  - JOUR
TI  - The effect of grain boundaries on magnetic exchange interactions in iron
AU  - Martin Zelený
AU  - Martin Heczko
AU  - Petr Šesták
AU  - Denis Ledue
AU  - Renaud Patte
AU  - Miroslav Černý
PY  - 2026
DA  - 2026/07/21
JO  - Journal of Physics D: Applied Physics
DO  - 10.1088/1361-6463/ae84dc
UR  - https://hal.science/hal-05775737v1
AB  - This work investigates how grain boundaries (GBs) modify magnetic exchange interactions in bcc iron, with particular focus on the effect of phosphorus segregation. Using density-functional theory combined with the Liechtenstein–Katsnelson–Antropov–Gubanov Green’s-function approach, we calculate Heisenberg exchange parameters for three symmetric tilt GBs, Σ5(310), Σ13(510), and Σ13(320), and use these parameters in Monte Carlo (MC) simulations to evaluate finite-temperature magnetic behavior. All clean GBs exhibit strong local deviations from bulk exchange interactions, including antiferromagnetic coupling across the boundary plane. These negative exchange interactions are not governed by interatomic distance alone, but arise primarily from the altered local coordination and symmetry breaking at the GB. Phosphorus segregation, modeled in both substitutional and interstitial configurations at the Σ5(310) GB, suppresses the antiferromagnetic couplings and significantly redistributes the local exchange landscape through chemical and electronic effects. MC results show that, despite pronounced local perturbations, realistic GB densities cause only a small reduction in the Curie temperature because bulk-like regions dominate the global magnetic transition. A substantial decrease in Curie temperature appears only when the GB volume fraction is artificially increased. The results demonstrate that GBs strongly influence local magnetic interactions while having a limited effect on global magnetic ordering, and they establish a general framework for linking atomistic interfacial structure and chemistry to mesoscale magnetic behavior in Fe-based materials.
SN  - 0022-3727
SN  - 1361-6463
ER  -

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