Spin-Fluctuation Mediated Thermal Conductivity Around the Magnetic Instability of CeNi2Ge2

Thermal conductivity has been measured from 0.03 K to 0.8 K in single crystal CeNi2Ge2which is quite near the quantum critical point (QCP). The Wiedemann–Franz law is observed at low temperatures (T<0.1 K) for both directions (j⊥c andj ∥ c), indicating that quasiparticles are scattered elastically asT→0 K. With increasing temperature, a deviation from the Wiedemann–Franz law due to inelastic spin-fluctuation contributions is observed. The effect of proximity to the QCP in CeNi2Ge2appears in the spin-fluctuation contributions to the thermal and electrical conductivities.