On the high-pressure phase diagram of YbRh2Si2

We studied the high-pressure phase diagram of YbRh2Si2 by AC calorimetry under high pressure up to 12 GPa. Two magnetic transitions are observed in the pressure range up to 7 GPa. The initial linear increase of the magnetic ordering temperature T-N with pressure is followed by a regime up to 8.5 GPa where valence fluctuations are important. Above 9 GPa TN is increasing as expected from the Doniach model. Further the influence of the local crystal electric field on the magnetic ordering is discussed. (c) 2006 Elsevier B.V. All rights reserved.