Direct capture and electrostatic repulsion in the self-assembly of rare-earth atom superlattices on graphene

Pivetta, Marina; Rusponi, Stefano; Brune, Harald

doi:10.1103/physrevb.98.115417

Cited by 25 publications

(21 citation statements)

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“…Upon adsorption on a surface, depending on the competition between atomic correction energy and surface binding energy [26], both divalent [27] and trivalent (6s 2 5d 1 4f n−1 ) [27,28] electronic configurations have been reported. In particular, on graphene, the RE adatom forms an ioniclike bond with the C atoms, resulting in a charge transfer of about one electron from the atom to graphene [29][30][31]. To a first approximation, this charge transfer TABLE I.…”

Section: Resultsmentioning

confidence: 99%

“…RE atoms were deposited from thoroughly degassed high-purity rods (99.9%) using an e-beam evaporator with a typical flux of 2 × 10 −3 monolayers (ML) per min, in a background pressure of 1 × 10 −10 mbar. The substrate temperature during deposition was approximately 10 K, a temperature at which surface diffusion is inhibited, resulting in a random spatial distribution of adatoms [29]. The STM images were acquired in constant-current mode with the tunnel voltage V applied to the sample [73].…”

Section: Appendix A: Experimental Methodsmentioning

confidence: 99%

“…Most of the protrusions (88% of the objects) have an apparent height between 450 and 500 pm at the tunneling parameters used (orange arrow). They are identified as clean Dy adatoms [24,29]. Owing to a large direct impingement area, many dimers are formed during deposition [29].…”

Section: Appendix C: Distinguishing Clean From Contaminated Re Atomsmentioning

confidence: 99%

“…They are identified as clean Dy adatoms [24,29]. Owing to a large direct impingement area, many dimers are formed during deposition [29]. They appear as lower (350 to 400 pm), slightly elongated objects (yellow arrow) and can be split by applying a tunnel voltage ramp [24].…”

Section: Appendix C: Distinguishing Clean From Contaminated Re Atomsmentioning

confidence: 99%

“…In addition to clean monomers and dimers, there are very few protrusions with apparent height similar to the one of dimers, but with round shape (green arrow), as well as some protrusions displaying even lower apparent heights (cyan and pink arrows). The percentage of monomers vs dimers depends on the coverage: For a coverage of 0.1% ML or less, exclusively monomers will be found [29]. The histogram in the bottom panel shows the occurrence of the different species (statistics on approximately 450 objects).…”

Section: Appendix C: Distinguishing Clean From Contaminated Re Atomsmentioning

confidence: 99%

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Measuring the Intra-Atomic Exchange Energy in Rare-Earth Adatoms

et al. 2020

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We present the first experimental determination of the intra-atomic exchange energy between the inner 4f and the outer 6s5d shells in rare-earth elements. Inelastic electron tunneling spectroscopy on individual rare-earth atoms adsorbed on metal-supported graphene reveals an element-dependent excitation, with energy between 30 and 170 meV, linearly increasing with the spin angular momentum of the 4f shell. This observation is possible owing to the strong spin polarization of the outer shells, characteristic of rare-earth adatoms on graphene. This polarization gives rise to a giant magnetoresistance of up to 75% observed for Dy on graphene=Irð111Þ single-atom magnets. Density functional theory calculations of the 6s5d shell spin polarizations and of their intra-atomic exchange constants with the 4f shell yield exchange energies in agreement with the experimental values. These results prove that the description of the spin dynamics in RE considering only the 4f − 5d interaction is oversimplified. A more realistic treatment requires us to consider a multishell intra-atomic exchange in which both 6s and 5d shells are taken into account, with the 4f − 6s contribution possibly prevailing over the 4f − 5d one. Our findings are important for the general understanding of magnetism in rare earths, whether they are in bulk compounds or as surface adsorbed atoms and clusters. The results presented here also push for a revision of the description of the spin dynamics in rare-earth-based systems.

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