Synthesis and Magnetization of New Room-Temperature Molecule-Based Magnets: Effect of Stoichiometry on Local Magnetic Structure by X-ray Magnetic Circular Dichroism

Abstract

The synthesis and the magnetic properties of two new bimetallic chromium−vanadium ferrimagnets, compounds 1 and 2, are reported. They belong to a set of nonstoichiometric Prussian blue analogues CIyV[CrIII(CN)6]z·nH2O (C, alkali cation) with TC varying between 295 and 315 K (TC = 310 K for 1 and 315 K for 2). They are obtained through mild chemistry from the molecular precursor [CrIII(CN)6]3- and from vanadium VII salts. The synthetic conditions determine (i) the oxidation state of the vanadium (VII, VIII, or VIV), (ii) the stoichiometry, and (iii) hence the magnetic properties. The reported systems present a larger magnetization than the first reported V−Cr analogue (0.36NAβ for 1 and 0.40NAβ for 2). Furthermore, X-ray magnetic circular dichroism (XMCD) data demonstrate (i) the short-range antiferromagnetic coupling between the spins borne by the chromium(III) and vanadium ions and (ii) the reversal of the local magnetization on vanadium and chromium when changing the stoichiometry.