Substituting Eu by Ca in ferromagnetic EuB6 leads to a percolation limited magnetic ordering. We present and discuss magneto-optical data of the Eu1−xCaxB6 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.
@article{arxiv.cond-mat/0510155,
title = {Magneto-optical evidence of double exchange in a percolating lattice},
author = {G. Caimi and A. Perucchi and L. Degiorgi and H. R. Ott and V. M. Pereira and A. H. Castro-Neto and A. D. Bianchi and Z. Fisk},
journal= {arXiv preprint arXiv:cond-mat/0510155},
year = {2012}
}