Electronic structure study of triangular lattices inFeGa2S4,Fe2Ga

Abstract

We have studied the electronic structure of the Fe and Ni triangular lattices in FeGa 2 S 4 , Fe 2 Ga 2 S 5 , and NiGa 2 S 4 using photoemission spectroscopy measurements, configuration-interaction calculations on FeS 6 and NiS 6 cluster models, and unrestricted Hartree-Fock calculations on FeS 2 and NiS 2 triangular lattices. The cluster-model analysis of the Fe 2p core-level spectra shows that the S 3p to Fe 3d charge-transfer energy ⌬ is ϳ2.5 eV in FeGa 2 S 4 and Fe 2 Ga 2 S 5 , in contrast to the small ⌬ ͑ϳ−1 eV͒ found in NiGa 2 S 4 . The relationship between the ⌬ value and the superexchange pathway has been examined using the unrestricted Hartree-Fock calculations. In FeGa 2 S 4 and Fe 2 Ga 2 S 5 , the superexchange interaction between the nearest-neighbor sites is dominant while that between the third-nearest-neighbor sites is enhanced in NiGa 2 S 4 .

Study of the Electronic Structure of NiGa2S4 and Extraction of the Spin Hamiltonian Parameters from Ab Initio Calculations

“…Periodic calculations were also performed to determine the band structure and the magnetic couplings. From local density approximation plus U (LDA+U) density functional theory (DFT) calculations, the magnetic couplings were estimated to be J 1 = –8.4 meV, J 2 = –0.3 meV, and J 3 = –4.1 meV, whereas unrestricted Hartree–Fock calculations gave J 1 = –12.0 meV, J 2 = –0.3 meV, and J 3 = –17.9 meV …”

Charge-Spin Correlation in van der Waals AntiferromagnetNiPS3

“…The corresponding ground state should be composed of t 2g 6 e g 3 electrons at Ni 3d orbitals and one hole at S 3p orbitals (L); i.e., t 2g 6 e g 3 L, with the 3 A 2g symmetry [50] (see Supplemental Materials (f) [30]). According to the NiS 6 cluster model, the lowest-energy ionization state was found to have 2 E g symmetry [50,57], and the corresponding state is clearly seen in XPS valence spectra (see Supplemental Materials (e-4) [30]). This suggests that peak A could be assigned as an inter-site transition between NiS 6 clusters that transfer an electron between two t 2g 6 e g 3 L ( 3 A 2g ) clusters.…”

Separation between Low-Energy Hole Dynamics and Spin Dynamics in a Frustrated Magnet

“…This observation shows that the topmost Ni 3d e g band has a peculiar band folding related to spin or charge correlations with Q E while a very flat Ni 3d e g band along the À-M direction is expected from the band calculations using both of a local-density-approximation calculation [21] and a model Hartree-Fock (HF) calculation [22]. In order to see detailed dispersions of the Ni 3d e g band, intensity plots along À-M and À-K directions are displayed in Figs.…”

“…(d) Excitonic coupling with Q E or Q 0 E between the upper and lower Hubbard bands. The upper and lower Hubbard bands are shown by the dots which are calculated by unrestricted Hartree-Fock approximation[22].…”