Low-temperature properties of CeAu2Ge2single crystals grown from Au-Ge and Sn flux

The specific heat of CeAu2Ge2 single crystals grown from Au-Ge (AGF) or Sn flux (SF) was measured at temperatures T between 1.8 and 200 K. Two magnetic transitions are observed in the zero-field specific heat at 12.1 and 14.5 K in the AGF sample, while only a single sharp transition at 9.2 K is seen in the SF sample, confirming our recent susceptibility results [Fritsch et al., Phys. Rev. B 84, 104446 (2011)]. We observe several field-induced transitions in the magnetoresistance of the AGF sample measured at 1.6 and 2.3 K in accordance with the B-T phase diagram constructed from isothermal magnetization curves M(B). In addition, we have measured M(B) under hydrostatic pressure P up to 10.5 kbar. The Neel temperature TN increases linearly with P at a small rate of 0.049 K/kbar, which suggests that, if TN(P ) is attributed to a pure volume effect, this compound is close to the maximum transition temperature of the Doniach diagram. The transition fields BM between the field-induced phases increase linearly with P as well. The comparable Gruneisen parameters of TN and BM indicate that the energy scale depending on the sample’s volume is given by the antiferromagnetic correlations and not by the Kondo effect. We discuss possible reasons for the different magnetic behavior of AGF and SF samples.