Magnetic phase separation in europium hexaboride and its relation to the Kondo interaction

Europium hexaboride single crystals have been investigated using the electron paramagnetic resonance at a frequency of 9.25 GHz in the temperature range 10–300 K. The magnetic phase separation of the spin system of europium ions Eu²⁺ is observed. The cause of the separation is the formation of the polarons of two types associated with the Kondo and anti-Kondo couplings of charge carriers of the valence and conduction bands, respectively, with the localized magnetic moments of Eu²⁺.