Low-temperature properties of CeAu₂Ge₂ single 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. 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 Néel temperature T_N increases linearly with P at a small rate of 0.049 K/kbar, which suggests that, if T_N(P) is attributed to a pure volume effect, this compound is close to the maximum transition temperature of the Doniach diagram. The transition fields B_M between the field-induced phases increase linearly with P as well. The comparable Grüneisen parameters of T_N and B_M 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.