Kondo effect and STM spectra through ferromagnetic nanoclusters

Gregory A. Fiete, Gergely Zarand, Bertrand I. Halperin, and Yuval Oreg
Phys. Rev. B 66, 024431 – Published 22 July 2002
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Abstract

Motivated by recent scanning tunneling microscope (STM) experiments on cobalt clusters adsorbed on single-wall metallic nanotubes [Odom et al., Science 290, 1549 (2000)], we study theoretically the size dependence of STM spectra and spin-flip scattering of electrons from finite size ferromagnetic clusters adsorbed on metallic surfaces. We study two models of nanometer size ferromagnets. (i) An itinerant model with delocalized s, p, and d electrons and (ii) a local moment model with both localized d-level spins and delocalized cluster electrons. The effective exchange coupling between the spin of the cluster and the conduction electrons of the metallic substrate depends on the specific details of the single-particle density of states on the cluster. The calculated Kondo coupling is inversely proportional to the total spin of the ferromagnetic cluster in both models and thus the Kondo temperature is rapidly suppressed as the size of the cluster increases. Mesoscopic fluctuations in the charging energies and magnetization of nanoclusters can lead to large fluctuations in the Kondo temperatures and a very asymmetric voltage dependence of the STM spectra. We compare our results to the experiments.

  • Received 13 December 2001

DOI:https://doi.org/10.1103/PhysRevB.66.024431

©2002 American Physical Society

Authors & Affiliations

Gregory A. Fiete1, Gergely Zarand1, Bertrand I. Halperin1, and Yuval Oreg2

  • 1Department of Physics, Harvard University, Cambridge, Massachusetts 02138
  • 2Weizmann Institute of Science, P.O. Box 26, Rehovot 76100, Israel

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Vol. 66, Iss. 2 — 1 July 2002

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