COEXISTENCE OF ANTIFERROMAGNETIC FLUCTUATIONS AND ORDERING IN (CE, LA)RU2SI2

The occurrence of a metamagnetic like transition below ≈15-8 K in the magnetization (M) of Ce1-xLaxRu2Si2 single crystals for H parallel to the easy tetragonal c-axis (maximum in ∂M/∂H at a field HM) is reported. This transition exists in both non-ordered (x = 0 and 0.05) and antiferromagnetically ordered (x = 0.1 and 0.13) materials. In the latter, the maximum in ∂M/∂H persists even below TN while two additional peaks grow at fields Ha and Hc (Ha < H c < HM) corresponding to steps in M (changes in the magnetic structure). The persistence of HM > Hc is ascribed to coexistence of magnetic fluctuations (similar to those observed for x = 0) and long range ordering below TN. © 1990.