Interplay of magnetism and superconductivity in CeCu2Si2 under hydrostaticpressure.

One point of interest of the heavy fermion superconductor CeCu2Si2 is the a pparent coexistence of superconductivity with a phase of magnetic origin, u sually called A-phase. We have studied the behaviour of the A-phase under h ydrostatic pressure. We find that it is progressively weakened, and has alm ost disappeared at a pressure of 3.2 kbar. We have also measured the upper critical held and find that close to the A-phase boundary, a maximum in the H-c2(T) curve appears. We have analysed the H-c2 data taking into account a temperature dependent susceptibility chi(T) Ln order to reproduce the beh aviour expected for antiferromagnetic order, the exchange integral must be negative, implying that in CeCu2Si2, H-c2 is enhanced by the Jaccarino-Pete r effect (C) 1999 Elsevier Science B.V. All rights reserved.