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.