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 Aagaard Thuesen; Stergios Piligkos; Høgni Weihe; Hannu Mutka; Oliver Waldmann; Peter Oppeneer; Jesper Bendix; Frithjof Nolting; Harald Brune

doi:10.1039/c2sc00794k

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 Aagaard Thuesen, Stergios Piligkos, Høgni Weihe, Hannu Mutka, Oliver Waldmann, Peter Oppeneer, Jesper Bendix, Frithjof Nolting, Harald Brune

Department of Chemistry

67 Citations (Scopus)

Abstract

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]·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 Δ_eff = 3 cm^-1. Density-functional theory calculations show that the Dy-Cr couplings originate from superexchange via the fluoride bridges.

Original language	English
Journal	Chemical Science
Volume	3
Issue number	4
Pages (from-to)	1024-1032
Number of pages	9
ISSN	2041-6520
DOIs	https://doi.org/10.1039/c2sc00794k
Publication status	Published - Apr 2012

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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. https://doi.org/10.1039/c2sc00794k

Dreiser, J, Pedersen, KS, Piamonteze, C, Rusponi, S, Salman, Z, Ali, ME, Schau-Magnussen, M, Thuesen, CA, 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, vol. 3, no. 4, pp. 1024-1032. https://doi.org/10.1039/c2sc00794k

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title = "Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster",

abstract = "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]·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.",

author = "Jan Dreiser and Pedersen, {Kasper Steen} and Cinthia Piamonteze and Stefano Rusponi and Zaher Salman and Ali, {Md. Ehesan} and Magnus Schau-Magnussen and Thuesen, {Christian Aagaard} and Stergios Piligkos and H{\o}gni Weihe and Hannu Mutka and Oliver Waldmann and Peter Oppeneer and Jesper Bendix and Frithjof Nolting and Harald Brune",

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doi = "10.1039/c2sc00794k",

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T1 - Direct observation of a ferri-to-ferromagnetic transition in a fluoride-bridged 3d–4f molecular cluster

AU - Dreiser, Jan

AU - Pedersen, Kasper Steen

AU - Piamonteze, Cinthia

AU - Rusponi, Stefano

AU - Salman, Zaher

AU - Ali, Md. Ehesan

AU - Schau-Magnussen, Magnus

AU - Thuesen, Christian Aagaard

AU - Piligkos, Stergios

AU - Weihe, Høgni

AU - Mutka, Hannu

AU - Waldmann, Oliver

AU - Oppeneer, Peter

AU - Bendix, Jesper

AU - Nolting, Frithjof

AU - Brune, Harald

PY - 2012/4

Y1 - 2012/4

N2 - 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]·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.

AB - 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]·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.

U2 - 10.1039/c2sc00794k

DO - 10.1039/c2sc00794k

M3 - Journal article

SN - 2041-6520

VL - 3

SP - 1024

EP - 1032

JO - Chemical Science

JF - Chemical Science

IS - 4

ER -

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

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