Structure and magnetic properties of (5BAP)_2 CuBr_4: magneto-structural correlations of layered S+1/2 Heisenberg antiferromagnets

摘要

The synthesis, structure and magnetic behavior of (5BAP)_2CuBr_4 are reported (5BAP=2-amino-5-bromopyridinium (5BAP)_2 CuBr_4 is a member of a family of CuX_4~(2-) (X=Cl, Br) compounds which form C-centered lattices with two-dimensional (2D) antiferromagnetic interactions. Crystallographic data: monoclinic, C2/c, a=13.28 A, b=8.719 A, c=16.11 A, #beta#=95.40, Z=4. The structure was solved by direct methods and refined to R=0.0346 (R_w=0.0827) for 1749 observed unique reflections and 105 parameters. The CuBr_4~(2-) ions exist as distorted tetrahedra and are related by centering parallel to the C-face giving rise to a square magnetic exchange of -6.94(6) K and indicate a transition to 3D order at 4.0(2) K. The effects of structural variations upon the magnetic properties of CuX_4~(2-) layered compounds are considered