Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d-4f molecular cluster
2012 (English)In: Chemical Science, ISSN 2041-6520, Vol. 3, no 4, 1024-1032 p.Article in journal (Refereed) Published
We report on the synthesis, crystal structure and magnetic characterisation of the trinuclear, fluoride-bridged, molecular nanomagnet [Dy(hfac)(3)(H2O)-CrF2(py)(4)-Dy(hfac)(3)(NO3)] (1) (hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone, py = pyridine) and a closely related dinuclear species [Dy(hfac)(4)-CrF2( py)(4)]center dot 1/2 CHCl3 (2). Element-specific magnetisation curves obtained on 1 by X-ray magnetic circular dichroism (XMCD) allow us to directly observe the field-induced transition from a ferrimagnetic to a ferromagnetic arrangement of the Dy and Cr magnetic moments. By fitting a spin-Hamiltonian model to the XMCD data we extract a weak antiferromagnetic exchange coupling of j -0.18 cm(-1) between the Dy-III and Cr-III ions. The value found from XMCD is consistent with SQUID magnetometry and inelastic neutron scattering measurements. Furthermore, alternating current susceptibility and muon-spin relaxation measurements reveal that 1 shows thermally activated relaxation of magnetisation with a small effective barrier for magnetisation reversal of Delta(eff) 3 cm(-1). Density-functional theory calculations show that the Dy-Cr couplings originate from superexchange via the fluoride bridges.
Place, publisher, year, edition, pages
2012. Vol. 3, no 4, 1024-1032 p.
IdentifiersURN: urn:nbn:se:uu:diva-172170DOI: 10.1039/c2sc00794kISI: 000301122000011OAI: oai:DiVA.org:uu-172170DiVA: diva2:513690