RKKY coupling between impurity spins in graphene nanoflakes

Karol Szałowski
Phys. Rev. B 84, 205409 – Published 10 November 2011

Abstract

We calculate the indirect charge carrier mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between magnetic impurities for two selected graphene nanoflakes containing four hexagonal rings in their structure, differing by their geometry. We describe the electronic structure of either charge-neutral or doped nanoflakes using the tight-binding approximation with the Hubbard term, which is treated within the molecular-field approximation. We find pronounced differences in the RKKY coupling energies, dependent on the placement of the pair of magnetic moments in the nanostructure and on the edge form. For an odd total number of electrons in the structure, we predict in some circumstances the existence of ferromagnetic coupling with leading first-order perturbational contribution, while for an even number of charge carriers the usual, second-order mechanism dominates. Therefore, doping of the nanoflake with a single charge carrier is found to be able to change the coupling from an antiferromagnetic to a ferromagnetic one for some geometries.

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  • Received 14 June 2011

DOI:https://doi.org/10.1103/PhysRevB.84.205409

©2011 American Physical Society

Authors & Affiliations

Karol Szałowski*

  • Department of Solid State Physics, University of Łódź, ulica Pomorska 149/153, PL-90-236 Łódź, Poland

  • *kszalowski@uni.lodz.pl

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Issue

Vol. 84, Iss. 20 — 15 November 2011

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