Magnetic properties of some transition-metal Prussian Blue Analogs with composition M3[M′(C,N)6]2·xH2O

Abstract

Magnetic data are reported for Prussian Blue Analogs (PBAs) of composition M3[M′(C,N)6]2·xH2O, where M = Mn, Co, Ni or Cu and M′ = Cr, Fe or Co and x is the number of water molecules per unit cell. PBAs crystallize in cubic framework structures, which consist of alternating MIIIN6 and MIIC6 octahedra. Occupancies of the octrahedra are not perfect: they may be empty and the charges are balanced by the oxygen atoms originating from guest water molecules at the lattice site (C or N site) or the interstitial site (between the octahedrals) of the unit cell. Large crystal-field splittings due to the octrahedral environment results in a combination of low- or high-spin configurations of localized magnetic bivalent and trivalent 3d moments. The magnetic susceptibility of studied PBAs follows the Curie–Weiss behavior in the paramagnetic region up to room temperature. Moreover, the data provide evidence for a long-range magnetic ground state for most metal hexacyanochromates and all metal hexacyanoferrates, while hexacyanocobaltates remain paramagnetic down to the lowest temperature measured (2 K). For all compounds, the effective magnetic moments determined from experiments were found to be in reasonable agreement with predicted combinations of high- and low-spin moments.

Keywords

• Prussian Blue Analogs
• Curie–Weiss behavior
• High-spin and low-spin magnetism
• Molecular magnetism
• Crystal fields