Remarks on quantum critical behavior in heavy fermions

Generalized scaling relations and renormalization group results are used to discuss the phase diagrams of heavy fermion systems. We consider the cases where these materials are driven to a magnetic quantum critical point either by applying external pressure or a magnetic field. The Ehrenfest equation relating the pressure derivative of the critical temperature to the ratio of thermal expansion and specific heat close to a magnetic quantum critical point (QCP) is analyzed from the scaling point of view. We consider different phase diagrams of antiferromagnetic heavy fermions in an external uniform magnetic field and the implication of renormalization group results for predicting their behavior.