The difference between and originates from the different placement of the Pt atoms in the sub-surface layer. The symmetry of both adsorption sites is C 3 v. We use the 3 × 3 × 1 supercell model with twenty seven Pt atoms (three layers), and the rare-earth adatom which is placed either in the or the hollow positions atop the Pt(111) surface (see supplemental Fig. Previously, the method was used to treat the 4 f-electron materials in paramagnetic phase 8, 18, and we extend it to the spin-polarized case.
#A.t.o.m. characters full
In this approach, the DFT electronic structure obtained by the relativistic version 14, 15 (with the spin-orbit coupling (SOC) included) of the full-potential linearized augmented plane wave method (FP-LAPW) 16 is consistently extended to account for the full structure of the 4 f-orbital atomic multiplets and their interaction with the conduction bands 17. Here, we report the charge self-consistent electronic structure theory of performed by combining DFT with the exact diagonalization (ED) 12 of a single-impurity Anderson model 13. It opens new opportunities to treat the electronic structure of complex materials containing RE elements. Recently, the combination of DFT with the dynamical mean field theory 9 in a form of the Hubbard-I approximation (HIA) 10 has been applied to the elemental RE, and is shown to be superior to the DFT+U and semiempirical ligand field (or equvalently crystal field) theory 11. While DFT+U can describe the chemical inertness of the 4 f shell, it does not include the atomic multiplet effects, and can yield ambiguous results for the magnetic moments, or valence stability 8. Their main role was to identify the most favorable adsorption site and the optimal height for the Ho adatom above the Pt surface layer. Up to date, conventional DFT and DFT+Coulomb U 6, 7 (DFT+U) methodologies were used in the calculations of 1, 3. Further analysis 5 critically reexamined the XMCD data analysis 2, and confirmed qualitatively the magnetically unstable ground state of Ho. The multiplet calculations 2 with the parameters chosen to reproduce the x-ray magnetic circular dichroism (XMCD) spectra resulted in | J = 8, J z = ☖〉 ground states. Theoretical calculations can shed light on the controversy concerning the magnetic state of The two | J = 8, J z = ☘〉 magnetic ground states pointing into and out of the Pt(111) surface were inferred from ab initio density functional theory (DFT) calculations 1. This indicates that the 4 f electrons do not contribute to the spin polarized tunneling processes in RE atoms on metals. Moreover, the newer IETS experimental data 3 did not see neither signatures of the spin-flip excitations nor spin-based telegraph noise for Ho atoms. However, the x-ray spectroscopy experiments 2 have shown that the ground state of Ho is magnetically unstable, with no magnetic remanence. Recent inelastic electron tunneling spectroscopy (IETS) measurements 1 reported the moment lifetime up to 700 s below 1 K temperature, due to the single-ion magnetic anisotropy.
There is an ongoing debate whether the magnetic moment on Ho atom on Pt(111) surface can be stable on the long time scale. The stable magnetic quantum state of the adatom was found on the time scale of 1500 s at 10 K temperature. The major advance of observing the magnetic remanence was recently reported for the Ho adatom on MgO substrate 4. These “single-atom” magnets serve as benchmarks in a quest for the ultimate size limit of magnetic information storage. The study of single magnetic rare-earth (RE) atoms adsorbed on metallic 1, 2, 3 and insulating 4 solid surfaces recently became a subject of intense research.
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