Anomalies of Heat Capacity and Phase Transitions in $Tm_{1-x}Yb_{x}B_{12}$

In the system $Tm_{1 - x}Yb_{x}B_{12}$ the specific heat has been studied in a wide range of Yb-concentration in the vicinity of the quantum critical point $x_{C}$ ≈ 0.3. The results were obtained on high quality single crystalline samples of $Tm_{0.7}Yb_{0.3}B_{12}$ compound placed near quantum critical point, both for antiferromagnetic metals (x < $x_{C}$) as well as for paramagnetic insulators (x > $x_{C}$) within a wide temperature range of 1.9-300 K in magnetic field up to 9 T. The temperature dependence of the magnetic contribution to specific heat for $Tm_{0.74}Yb_{0.26}B_{12}$ shows a logarithmic divergence of the form $C_{mag}$/T∿-lnT at T<4 K, which may be attributed to the quantum critical regime, and it is suppressed by strong external magnetic field. The Schottky anomaly of the magnetic contribution to specific heat in $Tm_{1 - x}Yb_{x}B_{12}$ has been established and analyzed in detail.