CeRu₂Si₂ and Quantum Critical Metamagnetism?

CeRu₂Si₂ is a well-known prototypical heavy fermion system and shows a sudden strong increase in the magnetization M and the sample length ΔL for magnetic fields parallel to the crystallographic c-direction at around 7.8 T. These anomalies occur below 4K and sharpen with decreasing temperatures, but no features for a first order phase transition are observed down to 15mK. We report new thermal expansion α, magnetostriction λ and specific heat C/T measurements, which have been made in mT magnetic field steps around the metamagnetic crossover down to 15mK on very pure single crystals. The results show hints for the existence of a quantum critical endpoint in CeRu₂Si₂ and were compared with an extended model of metamagnetic quantum criticality, which was first introduced by Millis et al. in 2002.