Pressure-Induced Successive Magnetic Phase Transitions in the Spin Gap System TlCuCl$_3$

TL;DR

This study investigates pressure-induced magnetic phase transitions in TlCuCl$_3$, revealing successive magnetic orderings and a spin reorientation at low temperatures under high hydrostatic pressure.

Contribution

It provides the first detailed neutron scattering analysis of pressure-induced magnetic phases and spin reorientation in TlCuCl$_3$, expanding understanding of quantum spin systems under pressure.

Findings

Pressure induces magnetic ordering at 16.9 K.

A spin reorientation occurs at 10 K.

Ordered moments lie in the a-c plane below T_N.

Abstract

Under the hydrostatic pressure $P=1.48$ GPa, polarized neutron elastic scattering experiments have been carried out on the coupled spin dimer system TlCuCl$_3$ with the gapped ground state at ambient pressure. Pressure-induced magnetic ordering occurs at the transition temperature $T_{\rm N}=16.9$ K. As in the field-induced and impurity-induced magnetic ordered phases, the ordered moments lie in the $a-c$ plane just below $T_{\rm N}$. An additional spin reorientation (SR) phase transition was observed at $T_{\rm SR}=10$ 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.