Abstract
Magnetization measurements under hydrostatic pressure were performed on an S=1⁄2 coupled spin dimer system TlCuCl3 with a gapped ground state under magnetic field H parallel to the [201] direction. With increasing applied pressure P, the gap decreases and closes completely at Pc=0.42±0.05 kbar. For P>Pc, TlCuCl3 undergoes antiferromagnetic ordering. A spin-flop transition was observed at Hsf\\simeq0.7 T. The spin-flop field is approximately independent of pressure, although the sublattice magnetization increases with pressure. The gap and Néel temperature are presented as functions of pressure. The occurrence of the pressure-induced quantum phase transition is attributed to the relative enhancement of the interdimer exchange interactions compared with the intradimer exchange interaction.
