Magnetic properties of S = 1/2 quasi-triangular lattice materials: Cu(2(1-x))Zn(2x)(OH)3NO3/(C7H15COO)·mH2O

We have investigated the structural and magnetic properties of two classes of spin S = 1/2 antiferromagnetic quasi-triangular lattice materials: Cu(2(1-x))Zn(2x)(OH)(3)NO(3) (0 ≤ x ≤ 0.65) and its long chain organic derivatives Cu(2(1-x))Zn(2x)(OH)(3)(C(7)H(15)COO)·mH(2)O (0 ≤ x ≤ 0.29). The series of layered structure compounds constitute a substitutional magnetic system, in which spin S = 1/2Cu(2+) ions and nonmagnetic Zn(2+) ions are arranged on a two-dimensional quasi-triangular lattice. For the nitrate compounds we found that the substitution of Zn(2+) ions can continuously decrease the Néel temperature, T(N), but never completely remove the magnetic order. In addition, the frustration effect in these materials is suppressed by a three-dimensional interlayer interaction. On the other hand, the corresponding long chain alkyl carboxylic acid group of intercalated materials, Cu(2(1-x))Zn(2x)(OH)(3)(C(7)H(15)COO)·mH(2)O, show spin-glass-like behavior, which is caused by the interplay of geometric frustration and mixed sign interactions. A tentative explanation for these findings is proposed in terms of a cluster-glass picture.