Search for a critical concentration from ferromagnetic to antiferromagnetic ground state in CeRu2(Si1-xGex)(2)

Thermal expansion, magnetization, and magnetostriction experiments performe d on CeRu2(Si1-xGex)(2) single crystals with 0.55 less than or equal to x l ess than or equal to 1 are reported. An antiferromagnetic (AF) ordering is always observed (T-N = 8.3 and 10.1 K for x = 1 and 0.55, respectively). Fo r x = 0.7 a ferromagnetic (FM) transition occurs. Te decreases rapidly from 7.5 K for x = 1, to 3 K for x = 0.7 and the AF area in the (B, T) plane in creases. The ground state remains AF for (0.06-0.07) less than or equal to a less than or equal to 0.6. A crystal with x = 0.65 should show T-C = 0. ( C) 2000 Elsevier Science B.V. All rights reserved.