Quantitative modeling of magnetic critical behavior in MCl2 (M = Ni, Fe) monolayers: The role of long-range exchange interactions and supercell size
Physica B: Condensed Matter, cilt.742, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 742
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.physb.2026.419304
- Dergi Adı: Physica B: Condensed Matter
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Compendex, INSPEC
- Anahtar Kelimeler: 2D magnetism, Cellular automaton, Curie temperature, DFT+U, Ising model
- Gazi Üniversitesi Adresli: Evet
Özet
Transition-metal dihalides (MX2) are a promising class of van der Waals magnets for spintronic and magnetic memory applications. However, theoretical predictions of their critical temperatures often deviate from experiment because insufficient supercell sizes fail to capture long-range exchange interactions. Here, a quantitatively reliable framework combining spin-polarized DFT + U calculations with an extended spin-S Ising model on a triangular lattice is developed for monolayer NiCl2 and FeCl2. A 4×4 supercell, identified as the minimum size required to include interactions up to the third-nearest neighbors (J1, J2, J3), was used to extract interaction parameters from multiple magnetic configurations. Spin-S Cellular Automaton simulations yielded Curie temperatures of 44.4 ± 0.5 K for NiCl2 and 21.8 ± 0.5 K for FeCl2, in close agreement with experiment, obtained with a single transferable, literature-based Hubbard U applied to both materials. The results confirm the decisive role of long-range interactions in describing two-dimensional magnetic behavior.