Structure of two-dimensional Fe3O4

Abstract

Paper published as part of the special topic on Oxide Chemistry and CatalysisOXIDE2020 ARTICLES YOU MAY BE INTERESTED IN Vibrational properties of CO 2 adsorbed on the Fe 3 O 4 (111) surface: Insights gained from DFT

Stability, magnetic order, and electronic properties of ultrathin Fe3O4 nanosheets

“…It should be noted that also the total energies of the FiM, AFM II, and mixed spin configurations are lower than the energies of the rocksalt and TOO films. These findings confirm that the atomic geometry associated with tetrahedral surface terminations is preferential, which is in agreement with recent experimental observations [14,15]. Thus, it is concluded that the phase stability of the TOT phase can be attributed to two mechanisms: (i) the reduced surface energy associated with the geometrical organization of the atoms associated with tetrahedrally coordinated surface layers and (ii) the reduction in surface energy owing to the transforma-tion in magnetic ordering from AFM II to AFM I, where the former represents the largest contribution to the stability.…”

“…Because surface elastic components of a close-packed (111) surface are isotropic [50], the observed positive in-plane relaxation strain shows that the surface stress components are tensile in character [51,52]. The optimized interplanar distance between the neighboring Fe layers of the AFM I configuration is 2.91 Å, which is in good agreement with the experimental value of about 2.9 Å obtained from surface x-ray diffraction measurements [15].…”

“…The spin configuration is found to have a small influence on the equilibrium lattice parameter, which is calculated to be a 0 = 3.21 Å for all cases. This value is 2.2% larger than the experimental value of 3.14 Å [15] and consistent with the overestimation of the bulk lattice constant.…”

“…Hence, the impact of the stacking sequence of the O layers on the total energy is small. Previous experimental results suggest that the x-ray rod profiles for the TOT1 phase are in very good agreement with the DFT + U data [15], whereas those of the TOT2 and TOT3 deviate somewhat. However, because of the similar energies of the TOT2 and TOT3 structures, we cannot exclude them based only on energetic arguments.…”

“…Suitable candidates for this purpose are silver substrates, which are relevant mainly for two reasons: (i) they interact weakly with both Fe and O and (ii) exhibit a low work function and electronegativity, which reduces the charge transfer between the film and the substrate. Through a series of recent experiments, the existence of a novel three-layered Fe 3 O 4 phase grown on a Ag(100) substrate has been confirmed [14,15]. This appears to be a distinct meta-stable form of Fe 3 O 4 with a thickness of about 1 nm.…”