Magnetic exchange in 2,2'-bipyridyliron(III) chloride

Abstract

The magnetic susceptibility and anisotropy of cis-bis(2,2'-bipyridyl)dichloroiron(III) tetrachloroferrate(III), cis-[Fe(bpy)₂Cl₂]⁺ [FeCl₄]-, have been measured between 1.8 and 300 K at magnetic fields up to 1 T. The magnetization on the cation and anion sites has been estimated by means of polarized neutron diffraction measurements at 1.5 and 4.6 T, and at temperatures from 2.1 to 41 K.

These magnetic results may be fitted to a 'mean-field' model of magnetic exchange in which the total exchange integral parameter, Σ_ijJ_ij, is c. -1.1 K. The magnetic results and structural details for the compound suggest that the strongest exchange pathway connects chains of alternating cations and anions. The inter-chain exchange is small. However, the substantial magnetic anisotropy and the much stronger decrease with temperature of the FeCl₄- ion site moment, relative to that of the cation, both indicate a complex magnetic exchange network and consequent magnetic behaviour. No sign of magnetic order is observed to at least 2.9 K.