Magnetic compensation and ordering in the bimetallic oxalates: why are the 2D and 3D series so different?

Although the exchange coupling and local crystal-field environment are almost identical in the two-dimensional (2D) and three-dimensional (3D) series of bimetallic oxalates, those two classes of materials exhibit quite different magnetic properties. Using mean-field theory to treat the exchange interaction, we evaluate the transition temperatures and magnetizations of the 3D Fe(II)Fe(III) and Mn(II)Cr(III) bimetallic oxalates. Because of the tetrahedral coordination of the chiral anisotropy axis, the 3D bimetallic oxalates have lower transition temperatures than their 2D counterparts, and much stronger anisotropy is required to produce magnetic compensation in the 3D Fe(II)Fe(III) compounds. The spin-orbit coupling with the non-collinear orbital moments causes the spins to cant in both 3D compounds.