Magnetic properties of Eu$_{0.9}$Yb$_{0.1}$B$_{6}$

The magnetic properties of substitutional solid solutions Eu$_{0.9}$Yb$_{0.1}$B$_{6}$ have been investigated in the temperature range of 2–300 K in fields up to 5 T. The data obtained confirm that the state with the electronic and magnetic phase separation (typical of europium hexaboride) is implemented in Eu$_{0.9}$Yb$_{0.1}$B$_{6}$ when the system metallization ($T_M\approx$ 15 K) precedes the ferromagnetic ordering ($T_C\approx$ 11.4 K). An analysis of the curves $M(H)$ in the Belov–Arrott coordinates makes it possible to evaluate spontaneous magnetization $M_{sp}$ and zero field susceptibility $\chi_0$ and determine the character of their critical behavior near the Curie point. The calculated critical indices ($\gamma\approx$ 1.28 and $\beta\approx$ 0.34) are in agreement with the predictions of the three-dimensional Heisenberg model.