A bromide analog of a one-dimensional Ising ferromagnet: trimethylammonium catena-bis(.mu.-bromo)diaquoiron(II) bromide

The crystal structure of the title compound, FeTAB, has been determined by X-ray diffraction and has been found to be isomorphous to that of the chloride analogue, FeTAC. The low-temperature magnetic susceptibility of polycrystalline samples can be modeled by using a one-dimensional ferromagnetic Ising model with a molecular field correction. The exchange parameters are estimated to be J/k=4 K and z'J'/k=−0.2 K, indicating that FeTAB has an intrachain exchange constant only one-fourth of that found in the chloride analogue while the interchain interactions are more than 10-time greater. Antiferromagnetic ordering is observed in the Mossbauer spectra near 1.3 K