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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·Z. Fisk
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Abstract

Substituting $Eu$ by $Ca$ in ferromagnetic $EuB_6$ leads to a percolation limited magnetic ordering. We present and discuss magneto-optical data of the $Eu_{1-x}Ca_{x}B_6$ 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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G. Caimi, A. Perucchi, L. Degiorgi, H. R. Ott, V. M. Pereira, A. H. Castro-Neto, A. D. Bianchi, Z. Fisk. 2005-10-06. Magneto-optical evidence of double exchange in a percolating lattice. https://doi.org/10.1103/physrevlett.96.016403

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