Magnetic phase diagram of UNi2Si2 under pressure

The influence of combined application of external hydrostatic pressure and a magnetic field parallel to the c-axis on the magnetic phases in UNi2Si2 w as studied by measuring electrical-resistivity anomalies related to magneti c phase transitions. As a result, the pressure evolution of the B-T magneti c phase diagram is presented. Both the magnetic field and the pressure prom ote the ground-state uncompensated antiferromagnetic phase at the expense o f the AF-I phase, which exists at higher temperatures. The value of the cri tical field for suppression of the AF-I phase becomes considerably reduced with increasing pressure. The applicability of the mean-field approach with in the axial Ising model for explaining pressure effects on magnetic phase transitions is discussed. (C) 2001 Elsevier Science B.V. All rights reserve d.