Structure and magnetism of the quasi-1-d K4Cu(MoO4)3 and the structure of K4Zn(MoO4)3.

Single crystals of K(4)Cu(MoO(4))(3) and nonmagnetic K(4)Zn(MoO(4))(3) have been grown by the flux-growth method. K(4)Cu(MoO(4))(3) can be described as a quantum quasi-1-d antiferromagnet with correlations between neighboring Cu(2+) ions but no magnetic long-range ordering down to 0.4 K. Comparison of the structure and magnetic properties of isostructural A(4)Cu(MoO(4))(3) (A = K, Rb) allows the isolation of the effects of low dimensionality from structural distortion along the Cu-O-Mo chains. The characteristic one-dimensional behavior is hence suppressed to lower the temperature in K(4)Cu(MoO(4))(3) in comparison with that of the Rb analogue. For example, a broad peak in the specific heat is observed ~2.3 K at 0 T, which is consistent with the onset of the quantum spin liquid state.