Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d-4f molecular cluster

Jan Dreiser, Kasper Steen Pedersen, Cinthia Piamonteze, Stefano Rusponi, Zaher Salman, Md Ehesan Ali, Magnus Schau-Magnussen, Christian Aa Thuesen, Stergios Piligkos, Høgni Weihe, Hannu Mutka, Oliver Waldmann, Peter Oppeneer, Jesper Bendix, Frithjof Nolting, Harald Brune

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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]·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 DyIII and CrIII 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 Δeff = 3 cm-1. Density-functional theory calculations show that the Dy-Cr couplings originate from superexchange via the fluoride bridges.
Original languageEnglish
JournalChemical Science
Issue number4
Pages (from-to)1024-1032
Publication statusPublished - 2012
Externally publishedYes

Cite this

Dreiser, J., Pedersen, K. S., Piamonteze, C., Rusponi, S., Salman, Z., Ali, M. E., Schau-Magnussen, M., Thuesen, C. A., Piligkos, S., Weihe, H., Mutka, H., Waldmann, O., Oppeneer, P., Bendix, J., Nolting, F., & Brune, H. (2012). Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d-4f molecular cluster. Chemical Science, 3(4), 1024-1032.