3D long-range magnetic ordering in layered metal-hydroxide triangular lattices 25 angstrom apart

The synthesis, characterization, and magnetic properties of the layered com pounds, Cu-2(OH)(3)(C12H25SO3) . H2O, Ni-2(OH)(3)(C-12,H25SO3) . H2O. and C o-5(OH)(8)(C12H25SO3)(2) . 5H(2)O, with a triangular magnetic lattice are r eported. The interlayer distances are 23.8 (Cu), 23.0 (Ni), and 25.8 Angstr om (Co). Long-range ferromagnetic (Ni) and ferrimagnetic (Co) ordering are observed with Curie temperatures of 18 (Ni) and 50 K (Co). The coercive fie lds are 400 (Ni) and 19,000 Oe (Co), the latter being among the hardest met al-organic magnets. The long-range ordering is interpreted as being due to dipolar interaction between layers with large effective moments as a conseq uence of precursor short-range intralayer interactions. The large coercive field is interpreted as resulting from a synergy of crystalline shape, surf ace, and single ion anisotropies. (C) 1999 Academic Press.