The ferromagnetic phase transition in EuB6: opticalevidence for quasiparticle undressing

The ferromagnetic phase transition in EuB6 at TC ¼ 15 K has been investigated by magneto-opticalmeasurements. A blue-shift of the plasma edge at ToTC in the reflectivity spectra characterizes this divalent rare-earth system. The data suggest dramatic changes in the electronic properties at the onset of the ferromagnetic order, indicative of an ongoing undressing of the quasiparticles as a driving mechanism for the ferromagnetic phase transition. r 2002 Elsevier Science B.V. All rights reserved.