Low-temperature thermal expansion and magnetostriction of YbRh2(Si1−xGex)2 (x=0 and 0.05)

Abstract We report a comparative study of the low-temperature thermal expansion and magnetostriction of the non-Fermi liquid (NFL) system YbRh2(Si1−xGex)2 (x=0 and nominally 0.05). The undoped compound (x=0) shows a sharp phase transition anomaly, related to antiferromagnetic ordering at T N =70 mK , that is suppressed by a small critical field B c =0.06 T (B⊥c). By contrast, very tiny anomalies at T N =(20±5) mK and B c =(0.027±0.005) T are observed in the x=0.05 system. The NFL behavior above TN is not affected by the Ge substitution.