Absence of a first-order metamagnetic transition inCeRu2Si2

Metamagnetic transition of the heavy-electron compound ${\mathrm{CeRu}}_2$ ${\mathrm{Si}}_2$ has been examined on high-purity single crystals by means of a static magnetization measurement at very low temperatures down to 90 mK. No hysteresis is observed in the magnetization process. The peak value of the differential susceptibility at the metamagnetic field ${\mathit{B}}_{\mathit{M}}$∼7.7 T follows a simple ${\mathit{T}}^2$ law below T∼0.5 K, and saturates to a finite value 1.88${\mathrm{\mu }}_{\mathit{B}}$/T Ce as T→0. From these results for two single crystals with slightly different quality, we have confirmed the nonexistence of a first-order phase transition at ${\mathit{B}}_{\mathit{M}}$ in the clean limit of this system. The itinerant nature of the 4f electrons is most likely preserved in the magnetized state at B≥${\mathit{B}}_{\mathit{M}}$.