Order to disorder transition in the XY-like quantum magnet Cs2CoCl4 induced by noncommuting applied fields

TL;DR

This study investigates how noncommuting magnetic fields influence the ground-state order of the quasi-one-dimensional XY-like antiferromagnet Cs2CoCl4, revealing a transition from ordered to spin liquid phases driven by quantum fluctuations.

Contribution

It provides the first detailed neutron diffraction analysis of field-induced order-disorder transitions in Cs2CoCl4 under noncommuting fields, identifying a spin liquid phase at high fields.

Findings

Long-range antiferromagnetic order exists below 217 mK in zero field.

Initial magnetic fields stabilize order via a spin-flop phase.

Higher fields induce a transition to a spin liquid phase.

Abstract

We explore the effects of noncommuting applied fields on the ground-state ordering of the quasi-one-dimensional spin-1/2 XY-like antiferromagnet Cs2CoCl4 using single-crystal neutron diffraction. In zero field interchain couplings cause long-range order below T_N=217(5) mK with chains ordered antiferromagnetically along their length and moments confined to the (b,c) plane. Magnetic fields applied at an angle to the XY planes are found to initially stabilize the order by promoting a spin-flop phase with an increased perpendicular antiferromagnetic moment. In higher fields the antiferromagnetic order becomes unstable and a transition occurs to a phase with no long-range order in the (b,c) plane, proposed to be a spin liquid phase that arises when the quantum fluctuations induced by the noncommuting field become strong enough to overcome ordering tendencies. Magnetization measurements confirm that saturation occurs at much higher fields and that the proposed spin-liquid state exists in the region 2.10 < H_SL < 2.52 T || a. The observed phase diagram is discussed in terms of known results on XY-like chains in coexisting longitudinal and transverse fields.