Pressure Effect on Transport Properties of EuNi(Si_(1-x)Ge_x)3 Compounds

摘要

The compounds of EuNi(Si_(1-x)Ge_x)3 order antiferromagnetically. At the temperature Tc below the Néel temperature Tn, EuNiSi3 (x= 0) shows an additional magnetic transition into ferromagnetic state. Tn decreases monotonously with increasing the Ge composition x. The Curie temperature Tc decreases rapidly with increasing x and vanishes at the critical composition x≈ 0.3. We have measured the electrical resistivity and thermopower of EuNi(Si_(0.8)Ge_(0.2))3, which is a compound near to the boundary between the ferromagnetic and antiferromagnetic ground states in the phase diagram for EuNi(Si_(1-x)Ge_x)3 system, under pressures up to 1.8 GPa at temperatures from 2 to 300 K. The anomalies in p(T) and S(T) curves of EuNi(Si_(0.8)Ge_(0.2))3 are observed at Tc= 16 K and Tn= 34 K at ambient pressure. Both T_C and Tn increase linearly with increasing pressure. The temperature variations of p and S of EuNi(Si_(0.8)Ge_(0.2))3 at P= 1.8 GPa are almost the same as those of EuNi(Sio.gGe_(0.1))3 (x=0.1) at ambient pressure, revealing that the effect of pressure on Tn and Tc is the same as that of the increase of Si concentration. The pressure and atomic composition dependences of the magnetic transition temperatures Tn and Tc can be expressed by using the Grüneisen parameters. These results indicate that the changes of Tn and Tc are attributed to the change of atomic volume induced by the applying pressure or the atomic substitution.