Europium underneath graphene on Ir(111): Intercalation mechanism, magnetism, and band structure

The intercalation of Eu underneath Gr on Ir(111) is comprehensively investigated by microscopic, magnetic, and spectroscopic measurements, as well as by density functional theory. Depending on the coverage, the intercalated Eu atoms form either a (2 x 2) or a ([radic]3 x [radic]3) R30[degrees] super...

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Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2014-12, Vol.90 (23), Article 235437
Main Authors: Schumacher, Stefan, Huttmann, Felix, Petrović, Marin, Witt, Christian, Förster, Daniel F., Vo-Van, Chi, Coraux, Johann, Martínez-Galera, Antonio J., Sessi, Violetta, Vergara, Ignacio, Rückamp, Reinhard, Grüninger, Markus, Schleheck, Nicolas, Meyer zu Heringdorf, Frank, Ohresser, Philippe, Kralj, Marko, Wehling, Tim O., Michely, Thomas
Format: Article
Language:English
Subjects:
Anisotropy
Condensed Matter
Dichroism
Doping
Electronic structure
Europium
Ferromagnetism
Graphene
Intercalation
Physics
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Summary:The intercalation of Eu underneath Gr on Ir(111) is comprehensively investigated by microscopic, magnetic, and spectroscopic measurements, as well as by density functional theory. Depending on the coverage, the intercalated Eu atoms form either a (2 x 2) or a ([radic]3 x [radic]3) R30[degrees] superstructure with respect to Gr. We investigate the mechanisms of Eu penetration through a nominally closed Gr sheet and measure the electronic structures and magnetic properties of the two intercalation systems. Their electronic structures are rather similar. Compared to Gr on Ir(111), the Gr bands in both systems are essentially rigidly shifted to larger binding energies resulting in n doping. The hybridization of the Ir surface state S sub(1) with Gr states is lifted, and the moire superperiodic potential is strongly reduced. In contrast, the magnetic behavior of the two intercalation systems differs substantially, as found by x-ray magnetic circular dichroism. The (2 x 2) Eu structure displays plain paramagnetic behavior, whereas for the ([radic]3 x [radic]3) R30[degrees] structure the large zero-field susceptibility indicates ferromagnetic coupling, despite the absence of hysteresis at 10 K. For the latter structure, a considerable easy-plane magnetic anisotropy is observed and interpreted as shape anisotropy.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.90.235437