Crossover from impurity-induced ordered phase to uniform antiferromagnetic phase under hydrostatic pressure in the doped spin-gap system TlCu${}_{1-x}$Mg${}_x$Cl${}_3$

Abstract

Magnetic phase transition under hydrostatic pressure in TlCu${}_{0.988}$Mg${}_{0.012}$Cl${}_3$ was investigated by magnetization measurements. The parent compound TlCuCl${}_3$ is a coupled spin dimer system, which undergoes a pressure-induced quantum phase transition from a gapped ground state to an antiferromagnetic state at $P_{\mathrm{c}}=0.42$ kbar due to the shrinkage of the gap. At ambient pressure, the present doped system exhibits impurity-induced magnetic ordering at $T_{\mathrm{N}}=2.5$ K. With increasing pressure, $T_{\mathrm{N}}$ increases. This is because the effective exchange interaction $J_{\mathrm{eff}}$ between unpaired spins is enhanced by the shrinkage of the gap. With a further increase in pressure, the present system undergoes a phase transition to a uniform antiferromagnetic phase due to the closing of the triplet gap in the intact dimers. The crossover from the impurity-induced ordered phase to the uniform antiferromagnetic phase occurs at $P\simeq 1.3$ kbar.

7 pages, 10 figures, submitted to Physical Review B

References in corpus (1)

• Bose-Einstein Condensation of Magnons in TlCuCl3: Phase diagram and specific heat from a self-consistent Hartee-Fock calculation with a realistic dispersion relation