ИСТИНА

Cuboid-shaped polyoxopalladates hosting either Fe3+ (3d5) or Co2+ (3d7) ions in their centre have been studied by means of x-ray absorption spectroscopy at the L3,2 absorption edges of the 3d element. While the x-ray absorption near-edge structure (XANES) contains already important information on the valence state, the x-ray magnetic linear dichroism (XMLD) and magnetic circular dichroism (XMCD) were used to refine the quantification of the crystal field related to the eight oxygen ions surrounding the central ion by comparison with simulations using the CTM4XAS program. In addition, spin and orbital magnetic moments were derived by a sum-rule based analysis of the XMCD. After a hydrogen plasma treatment, the Fe ions were reduced from 3d5 to a 3d6 state while the Co 3d7 state remains unaffected. However in both cases, drastic changes of the crystal field and the magnetic properties were obtained pointing to a possible application in nanoscale hydrogen sensing or storage devices. In addition, data of re-oxidised samples are presented and the influence of different heterogroups stabilising the polyoxopalladates is discussed.