Pressure effect on the ferromagnetism of an off-center rattling system Eu8Ga16Ge30

We report the pressure effect on the ferromagnetism of type-I clathrate Eu8Ga16Ge30 with T-C = 36 K by means of the resistivity rho and Hall coefficient R-H measurements. With increasing pressure up to 11.4 GPa, T-C increases up to 45 K. The concomitant decrease of rho is attributed to the increase of the carrier concentration because the normal part of R-H decreases with the ratio of -3.5%/GPa. At ambient pressure, rho(T) has broad peak at T*=23 K. Upon pressurizing, the peak is weakened but remain visible at T*=27 K even at P=11.4 GPa. Our findings suggest that the anomaly at T* is not so sensitive to the cage size up to 11 GPa, where the cage volume is compressed to 87% of the value at ambient pressure.