Pressure-Induced Successive Magnetic Phase Transitions in the Spin Gap System TlCuCl₃

Abstract

Under the hydrostatic pressure P=1.48 GPa, polarized neutron elastic scattering experiments have been carried out on the coupled spin dimer system TlCuCl₃ with the gapped ground state at ambient pressure. Pressure-induced magnetic ordering occurs at the transition temperature T_N=16.9 K. As in the field-induced and impurity-induced magnetic ordered phases, the ordered moments lie in the a–c plane just below T_N. An additional spin reorientation (SR) phase transition was observed at T_SR=10 K, where the ordered moments start to incline toward the b-axis. The temperature variations of the direction and the magnitude of the ordered moments were also investigated.