Tetragonal mixed system Cs₂CuCl_(4-x)Br_x complemented by the tetragonal phase realisation of Cs₂CuCl₄

Realisation of the tetragonal phase of $Cs_2CuCl_4$ is possible using specific crystal growth conditions at a temperature below $281K$. This work deals with the comparison of the magnetic susceptibility and the magnetization of this new tetragonal compound with the magnetic behaviour of tetragonal $Cs_2CuCl_{2.9}Br_{1.1}$, $Cs_2CuCl_{2.5}Br_{1.5}$, $Cs_2CuCl_{2.2}Br_{1.8}$ and presents consistent results for such quasi $2-D$ antiferromagnets. Structural investigation at low temperature for $Cs_2CuCl_{2.2}Br_{1.8}$ shows no phase transition. The structure remains in the tetragonal symmetry $I4/mmm$. Furthermore, several magnetic reflections corresponding to the propagation vector $k = (0, 0, 0)$ are observed for this tetragonal compound through neutron diffraction experiments below the magnetic phase transition at $T_N = 11.3K$ confirming its antiferromagnetic nature.