Structure and Magnetism of the Quasi-1-d K₄Cu(MoO₄)₃ and the Structure of K₄Zn(MoO₄)₃

Single crystals of K4Cu(MoO4)3 and nonmagnetic K4Zn(MoO4)3 have been grown by the flux-growth method. K4Cu(MoO4)3 can be described as a quantum quasi-1-d antiferromagnet with correlations between neighboring Cu2+ ions but no magnetic long-range ordering down to 0.4 K. Comparison of the structure and magnetic properties of isostructural A4Cu(MoO4)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 K4Cu(MoO4)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.