Magneto-Optical Evidence of Double Exchange in a Percolating Lattice

G. Caimi, A. Perucchi, L. Degiorgi, H. R. Ott, V. M. Pereira, A. H. Castro Neto, A. D. Bianchi, and Z. Fisk
Phys. Rev. Lett. 96, 016403 – Published 5 January 2006

Abstract

Substituting Eu by Ca in ferromagnetic EuB6 leads to a percolation limited magnetic ordering. We present and discuss magneto-optical data of the Eu1xCaxB6 series, based on measurements of the reflectivity R(ω) from the far infrared up to the ultraviolet, as a function of temperature and magnetic field. Via the Kramers-Kronig transformation of R(ω) we extract the complete absorption spectra of samples with different values of x. The change of the spectral weight in the Drude component by increasing the magnetic field agrees with a scenario based on the double-exchange model, and suggests a crossover from a ferromagnetic metal to a ferromagnetic Anderson insulator upon increasing Ca content at low temperatures.

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  • Received 6 October 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.016403

©2006 American Physical Society

Authors & Affiliations

G. Caimi1, A. Perucchi1, L. Degiorgi1, H. R. Ott1, V. M. Pereira2,3, A. H. Castro Neto2, A. D. Bianchi4,5, and Z. Fisk6

  • 1Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Switzerland
  • 2Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA
  • 3CFP and Departamento de Física, Faculdade de Ciências Universidade de Porto, 4169-007 Porto, Portugal
  • 4National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
  • 5Hochfeldlabor Dresden, Forschungszentrum Rossendort, Postfach 510119, D-01314 Dresden, Germany
  • 6Department of Physics, University of California, Davis, California 95616, USA

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Issue

Vol. 96, Iss. 1 — 13 January 2006

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