From heavy fermion antiferromagnetism to localized ferromagnetism: competition of two ground states in CeRu₂Ge₂on cooling

Abstract

Resistivity, specific heat and neutron scattering measurements performed on single crystals of CeRu2Ge2 are reported. The intrinsic behaviour of this compound is to exhibit a double transition from a paramagnetic to an antiferromagnetic and then a ferromagnetic state on lowering the temperature with TN = 8.3 K and respectively TC = 7.5 K. For the first time the antiferromagnetic order is characterized by neutron scattering. The propagation vector of the sine-wave modulated structure is k = (0.31,0,0) as in the Si doped compounds. This phase is found to be easily weakened by disorder, but an antiferromagnetic moment as large as 1.5 µB develops between TN and TC for the best crystal.