A Novel Molecular Assembly of a Cobalt–Sulfate Coordination Polymer and Melamine: A Manifestation of Magnetic Anisotropy

A novel molecular
assembly of a cobalt–sulfate coordination
polymer and melamine is synthesized under acidic conditions. Bar-shaped
pink monocrystals as long as 1 mm are found to align along magnetic
field lines in the proximity of a strong magnet. Magnetometry shows
no hysteresis at temperatures down to 2 K but instead magnetic anisotropy
and antiferromagnetic coupling. X-ray diffraction on a single crystal
reveals that the cobalt–sulfate chains are along the shortest
lattice vector or the crystal’s long axis. The crystal alignment
along the magnetic flux can be attributed to single-ion anisotropy
that results in longitudinal antiferromagnetic coupling along the
chain. Both structurally and magnetically isotropic crystals of metal–organic
hybrid materials can be highly useful as elemental components in magneto-optics.