A Dilute Three-Dimensional XY Ferromagnet

Iron(III) bis(diselenocarbamate) chloride is a pentacoordinate molecular ferromagnet ordering near 3.4 K. The unusual site symmetry yields a spin 3/2 ground state. A rather substantial zero-field splitting occurs, with D positive, leading to XY like magnetic properties at low temperature. Significant exchange interactions occur between molecules via Fe-Se...Se-Fe contacts, without substantial spatial anisotropy. It is of interest to examine the effects of diamagnetic dilution on such a system. We have succeeded in dissolving modest amounts of diamagnetic Zn(II) bis(dithiocarbamate) into the Fe(III) system lattice. Analysis of susceptibility and magnetization data reveals a sizable reduction of the magnetic ordering temperature of the pure material on dilution. Comparisons are possible with previous work in which dilution of the approximate 3D-Ising system Fe(III) bis(dithiocarbamate) chloride was studied. *Supported by NSF-Solid State Chemistry-Grant No. DMR-0085662 and by a grant from the Petroleum Research Fund of the American Chemical Society.