Toward Quantitative Magnetic Information from Transition Metal K-Edge XMCD of Prussian Blue Analogs

Two series of Prussian blue analogs (PBA) were used as model compounds in order to disentangle the information contained in X-ray magnetic circular dichroism (XMCD) at the K-edges of transition metals. The number of 3d electrons on one site of the bimetallic cyanide polymer has been varied by associating to the [Fe(CN)₆]^3- or the [Cr(CN)₆]^3- precursors various divalent metal ions A²⁺ (Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, and Cu²⁺). The compounds were studied by X-ray diffraction and SQUID magnetometry, as well as by X-ray absorption spectroscopy and XMCD at the K-edges of the A²⁺ transition metal ion. The study shows that the 1s → 4p contribution to the A K-edge XMCD signal can be related to the electronic structure and the magnetic behavior of the probed A²⁺ ion: the shape of the signal to the filling of the 3d orbitals, the sign of the signal to the direction of the magnetic moment with respect to the applied magnetic field, the intensity of the signal to the total spin number S_A, and the area under curve to the Curie constant C_A. The whole study hence demonstrates that PBAs are particularly well-adapted for understanding the information contained in the transition metals K-edge XMCD signals. It also offers new perspectives toward the full disentangling of the information contained in these signals and access to new insights into materials magnetic properties.