Quasi-one-dimensional anisotropic Heisenberg model in a transverse   magnetic field
  The phase diagram of weakly coupled $XXZ$ chains in a transverse magnetic field is studied using the mean-field approximation for the interchain coupling and known exact results for an effective one-dimensional model. Results are applied to the quasi-one-dimensional antiferromagnet $Cs_{2}CoCl_{4}$ and the value of interchain interaction in this compound is estimated. 
D.V.Dmitriev, V.Ya.Krivnov