High-field magnetization studies of two-dimensional copper antiferromagnets

The magnetic susceptibilities and high-field magnetization data for members of two families of S = 1/2, two-dimensional, square antiferromagnetic latt ices are reported. The known compounds bis-2-amino-5-methylpyridinium tetra bromocuprate, 1, and bis-2-amino-5-chloropyridinium tetrabromocuprate, 2, c rystallize in the space group C2/c with the tetrabromocuprate ions related by the C-centering and unit cell translations, leading to a square magnetic lattice. Similarly bispyrazinecopper(II) perchlorate, 3, and bispyrazineni tratocopper(II) hexafluoro-phosphate, 4, crystallize in the space groups C2 /m and I4/mcm respectively and also generate square magnetic lattices. High -field magnetization studies, up to 60 Tesla, have determined their saturat ion fields to be 21 T (1), 27 T (2), 53 T (3) and 32 T (4). All show upward curvature in plots of magnetization as a function of field and fall on a u niversal curve in good agreement with recent theoretical predictions.