Divergence of the grüneisen parameter and magnetocaloric effect at heavy fermion quantum critical points

Abstract

At any pressure sensitive quantum critical point (QCP) the thermal expansion is more singular than the specific heat leading to a divergence of the Grüneisen parameter. For a magnetic field sensitive QCP, the complementary property is the magnetic Grüneisen ratio which equals the magnetocaloric effect. Here we use both properties to investigate magnetic QCPs in different heavy fermion (HF) metals starting from CeNi 2Ge 2. The influence of dimensionality on quantum criticality is addressed by the comparison of cubic CeIn 3-x Sn x with layered CeMIn 5-x Sn x (M = Co, Rh) systems, in which Sn doping both acts as tuning parameter and introduces slight disorder. Near the field-tuned QCP in undoped CeCoIn 5 a crossover scale T* is discovered which separates 2D (at T>T*) from 3D (at T