Pressure-Induced Reentrant Oblique Antiferromagnetic Phase in Spin Dimer System TlCuCl_3

TL;DR

This study investigates pressure-induced magnetic phase transitions in TlCuCl_3, revealing a reentrant oblique antiferromagnetic phase caused by competing anisotropic energies, with detailed phase behavior under varying temperature and magnetic field.

Contribution

It provides the first detailed experimental and theoretical analysis of the reentrant oblique antiferromagnetic phase in TlCuCl_3 under high pressure.

Findings

Observation of antiferromagnetic ordering at 16.7 K under 1.4 GPa

Identification of a spin reorientation transition at 9.2 K

Detection of a second-order phase transition from OAF to SF phase

Abstract

Magnetization measurements under a hydrostatic pressure of P = 1.4 GPa were performed on the coupled spin dimer system TlCuCl_3, which exhibits a pressure-induced quantum phase transition from a gapped singlet state to an antiferromagnetic state at P_c = 0.042 GPa. Antiferromagnetic ordering with ordered moments parallel to the ac plane was observed at T_N = 16.7 K at 1.4 GPa. The spin reorientation phase transition was observed at T_R ~ 9.2 K for zero magnetic field, at which the ordered moments start to incline towards the b axis. With increasing external field parallel to th b axis, a second-order phase transition from the oblique antiferromagnetic (OAF) phase to the spin-flop (SF) phase occurs below T_R. We argue that the OAF phase arises from the competition between the anisotropic energies of the conventional second order and the fourth order, that increases with increasing pressure. We discuss the OAF-SF transition within the framework of the mean field approximation.