Anomalous Transport Properties of Carbon-Doped $EuB_6$

In the presented work we report electrical, magnetic and thermal properties of $EuB_{6-x}C_{x}$ single crystals with an estimated value of x ≈ 0.07. Our studies reveal an antiferromagnetic phase transition at $T_{N}$ ≈ 6.7 K. Electrical resistivity at zero magnetic field shows a pronounced resistivity maximum at $T_{M}$ ≈ 7 K, just above the antiferromagnetic phase transition temperature. With increasing applied magnetic field the maximum moves to lower temperature and becomes totally suppressed at the field of 9 T. Observed magnetoresistance is negative in the whole studied temperature range 2-20 K, yielding a ratio of ρ(0 T, 7 K)/ρ(9 T, 7 K) ≈ 2.5. The origin of such magnetoresistance is associated with formation of mixed magnetic structure in the system due to fluctuation of carbon concentration.