ИСТИНА

It is well-known that bulk palladium is paramagnetic, but it is also theoretically predicted that palladium can change its magnetic state under structural transformations. Recent studies have shown that palladium magnetism can be observed in Pd films, nanoparticles and nanowires [1]. Here, we investigated palladium in polyoxopalladates (POPs) nanoclusters. POPs form a new class of nanoscale materials with unique physical and chemical properties. These properties give them high potential for applications in catalysis and nanotechnology. POPs are polyatomic anionic clusters consisting of Pd(II) ions which are linked together by shared oxygen ions and RXO3n- groups. An example of this class presented in the current study is [PdII13AsV8O34(OH)6]8- palladate, denoted as Pd-Pd12. In this species the central Pd ion is surrounded by eight oxygens. The twelve palladium(II) ions in the outer shell are coordinated by four oxygen ions in a square planar geometry. Replacing the central palladium(II) ion by iron(III) (see in Fig. 1) or cobalt(II) ions while maintaining the symmetry and number of the palladium(II) ions in the outer shell gave us the possibility to distinguish the contributions from the central and outer shell palladium ions. This has been done by element- and in principle site-specific soft x-ray magnetic circular dichroism (XMCD) technique at the palladium M3,2 absorption edges and iron and cobalt L3,2 absorption edges as well. Particular features of XMCD and XANES spectra of palladium ions in different local environments were explained through comparison with results of multiplet calculations performed by the CTM4XAS program [3]. The crystal field parameters and the valence state of the central ion were quantified. In addition the influence of a soft hydrogen plasma treatment on the palladium magnetism was investigated. The work was funded by Helmholtz Association (Young Investigator’s group “Borderline Magnetism”, VH-NG-1031). [1] A. Delin, E. Tosatti, R. Weht, Phys. Rev. Lett., 92 (2004) 057201. [2] M. Barsukova-Stuckart, N.V. Izarova et al, Inorg. Chem., 18 (2012) 6167-6171. [3] E. Stavitski, F.M.F. de Groot, Micron, 41 (2010) 687-694.