Fabrication and magnetic properties of 4SC(NH₂)₂-Ni_0.97Cu_0.03Cl₂ single crystals

Single crystals of 4SC(NH₂)₂-Ni_1-xCu_xCl₂ (x=0.03) (Cu-DTN) containing spin S=1/2 Cu²⁺ and S=1 Ni²⁺ cations are synthesized by slow evaporation methods. Structural characterization demonstrates that the Cu-DTN is of a tetrahedral structure with lattice parameter c being 9.0995 Å, which is 1.32% expansion compared with that of parent material DTN due to the larger radius of the Cu ion. Direct current (DC) susceptibility measurements show that both the antiferromagnetic exchange interaction at low temperature and the large anisotropy of susceptibilities are suppressed after doping the Cu ion, which could be related to the structural distortion and the increase of the super-exchange paths in Cu-DTN.