  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.
