Magnetism of Cr10 wheels on Au(111) and Cu(111) surfaces

Trabajo presentado al X Meeting de GEFES (División de Física de la Materia Condensada de la Real Sociedad Española de Física), celebrado en Valencia del 24 al 26 de enero de 2018
We report on the magnetic properties of {Cr10} wheels (Cr10(OMe)20(O2CCMe)10) UHVsublimated on Cu(111) and Au(111) single-crystals investigated by means of by XAS & XMCD, SQUID magnetometry and STM. We discuss the magnetic anisotropy and magnetic moment field-dependence of the grafted {Cr10} molecules, as a function of the metallic substrate and layer thickness, and compare it with bulk material. Our results demonstrate that evaporated molecules show negligible anisotropy and weak dependence with the substrate. A combination of XMCD and SQUID magnetometry show that Mono- and Multilayer {Cr10} samples exhibit a magnetic behavior stemming from a S = 9 ground state, ruling out some previous results. Montecarlo simulations show that the magnetic evolution can be explained by {Cr10} molecules magneticaly consisting of two semi-crowns containing 4 Cr ions interacting ferromagnetically, separated by 2 Cr ions with antiferromagnetic interactions, giving rise to the ground S = 9 state, in agreement with previous EPR data in literature. Evaporation of {Cr10} onto a substrate producing subtle structural changes induce strong changes in the Cr-Cr interactions and distinct magnetic behavior from the bulk.