Dresden 2017 – scientific programme

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MA: Fachverband Magnetismus

MA 35: Magnetic Particles / Clusters

MA 35.8: Talk

Wednesday, March 22, 2017, 11:15–11:30, HSZ 101

Changing the magnetism of eightfold coordinated 3d transition metal ions in polyoxopalladates by hydrogen plasma — Nataliya Svechkina¹, Natalya V. Izarova¹, Detlef Schmitz², Alevtina Smekhova¹, and •Carolin Schmitz-Antoniak¹ — ¹FZ Jülich (PGI-6) — ²HZB, Berlin

Cuboid-shaped polyoxopalladates hosting either Fe³⁺ (3d⁵) or Co²⁺ (3d⁷) ions in their centres have been studied by means of x-ray absorption spectroscopy at the L_3,2 absorption edges of the 3d elements. 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 x-ray 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 the 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.