Inducement of non-Fermi-liquid behavior with magnetic field in heavy-fermion antiferromagnets

We present specific heat C(T) measurements down to T = 60 mK in magnetic fields up to B = 30 T for antiferromagnetic (afm) ordered heavy-fermion compounds CePd2Si2, CePtSi1-xGex (x greater than or equal to 0.2) and CeCu6 - xAgx (x greater than or equal to 0.1). In these systems a quantum critical point with typical non-Fermi-liquid (nFl) properties can be reached via pressure or concentration variation. After suppressing the afm order to T-N = 0 by applying a magnetic field on CePd2Si2 and CePtSi0.4Ge0.6, no such nFl properties are observed. In contrast to this, significant spin fluctuations in a CeCu5.2Ag0.8 single crystal are still present in a critical magnetic field parallel to the c-axis such that T-N --> 0 and nFl behavior is found from 3 K down to 0.06 K. (C) 1999 Elsevier Science B.V. All rights reserved.