Stabilization of Short- and Long-Range Magnetic Ordering through the Cooperative Effect of 1D [CuO 4 ] ∞ Chains and [CuO 2 X 2 ] Quadrilateral in Quasi-1D Spin-1/2 Systems.

Quasi-1D chain antiferromagnets with reduced structural dimensionality are a rich playground for investigating novel quantum phenomena. We report the synthesis, crystal structure, and magnetism of two novel quasi-1D antiferromagnets, β-PbCu 2 (TeO 3 ) 2 Cl 2 (I) and PbCu 2 (TeO 3 ) 2 Br 2 (II). Their magnetic frameworks are constructed via Cu-based quasi-1D [Cu(2)O 4 ] ∞ zigzag chains with square-planar [Cu(1)O 2 X 2 ] (X=Cl or Br) separated among 1D chains. Specific heat measurements show λ peaks at ~9 K and ~19 K for I and II, respectively. Moreover, both broad maximums (χ max =90 K for I and 80 K for II) and small kinks (T N ≈9 K for I and 19 K for II) have been observed in magnetic susceptibility measurements of I and II. Bonner-Fisher model fitting, and theoretical analyses were performed to evaluate the magnetic exchange interactions. Our experimental and theoretical results and structure-properties relationship analysis reveal the coexistence of short- and long-range magnetic ordering from the cooperative effect of 1D [CuO 4 ] ∞ chains and [CuO 2 X 2 ] quadrilateral.