The transition metal coordination compound $\mathrm{Fe}(\mathrm{pyrimidine}{)}_2{\mathrm{Cl}}_2$ crystallizes in a chiral lattice, space group ${I4\mathrm{}}_{1}22$ (or ${I4\mathrm{}}_{3}22).$ Combined magnetization, Mössbauer spectroscopy, and powder neutron diffraction studies reveal that it is a canted antiferromagnet below $T_N=6.4\mathrm{}\mathrm{K}$ with an unusually large canting of the magnetic moments of $14°$ from their general antiferromagnetic alignment, one of the largest reported to date. This results in weak ferromagnetism with a ferromagnetic component of $\sim 1{\mu }_B.$ The large canting is due to the interplay between the antiferromagnetic exchange interaction and the local single-ion anisotropy in the chiral lattice. The magnetically ordered structure of $\mathrm{Fe}(\mathrm{pyrimidine}{)}_2{\mathrm{Cl}}_2,$ however, is not chiral. The implications of these findings for the search of molecule based materials exhibiting chiral magnetic ordering are discussed.

• Received 6 February 2003

DOI:https://doi.org/10.1103/PhysRevB.69.134427