Hyperfine Interactions And Spin Dynamics In The Cr7fe(Ii) Antiferromagnetic Wheel Probed By Moessbauer Spectroscopy (Contributo in atti di convegno)

Type
Label
  • Hyperfine Interactions And Spin Dynamics In The Cr7fe(Ii) Antiferromagnetic Wheel Probed By Moessbauer Spectroscopy (Contributo in atti di convegno) (literal)
Anno
  • 2008-01-01T00:00:00+01:00 (literal)
Alternative label
  • Lantieri M., Cianchi L., Del Gallo F., Moretti P., Spina G., Timco G.A., Tuna F., Winpenny R.E. (2008)
    Hyperfine Interactions And Spin Dynamics In The Cr7fe(Ii) Antiferromagnetic Wheel Probed By Moessbauer Spectroscopy
    in ICMM, Firenze
    (literal)
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  • Lantieri M., Cianchi L., Del Gallo F., Moretti P., Spina G., Timco G.A., Tuna F., Winpenny R.E. (literal)
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  • Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM). (literal)
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  • The molecules belonging to a recently synthesized family of heterometallic wheels, which contain an even number of different antiferromagnetically coupled metallic ions, have a S`0 spin ground state . In order to set up the best conditions to synthesize \"good\" molecular magnets it is important to know the contribution of each metallic ion to the total spin . Mössbauer spectroscopy is an excellent local probe for the study of the magnetic properties of molecules containing iron. Here we present a Mössbauer analysis for the determination of the effective spin of the Fe(II) ion in the molecular nanomagnet [(n-C4H9)2NH2][Cr7Fe(II)F8(OOCCMe3)16] (Cr7Fe(II) in short). The magnetic core of the ring is formed by seven Cr(III) and one Fe(II) ions, arranged in an almost coplanar structure with antiferromagnetic nearest neighbours coupling. The nanomagnet has S = 1/2 ground state, due to the Cr(III)’s s = 3/2 spins and to the Fe(II) s = 2 one. Magnetization measurements in the range [0–7] T, which were performed at 2 and 4 K, and susceptibility measurements with 0.1, 0.5 and 1 T field between 2 and 300 K agree with S=1/2 ground state. Due to the low molecular percentage weight of Fe(II) in the compound, the Mössbauer sample was prepared by using H 95% 57Fe–enriched iron. In order to prevent texture effects, the target was made by mixing the compound with alumina. We tested the crystallites orientation in the sample by performing X ray-diffraction analysis, which showed a completely random orientation. Fourteen Mössbauer spectra were collected in the range (1.8, 15) K, displaying a very high resolution due to the mentioned 57Fe enrichment. Below 4 K the spectra are characterized by two wide lines, each showing a magnetic hyperfine sub-structure, which evolves with the temperature. Over 4 K, the two lines lead to collapse to a well–defined sharp quadrupolar doublet, typical of Fe(II) ion. We obtained the magnetic hyperfine tensor from the analysis of the lowest T spectra; moreover, from the T–evolution of the whole set of spectra we are able to determine the temperature dependence of the dynamic properties of the magnetization, which could be eventually compared to the spin dynamics probed by different experimental techniques . (literal)
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  • 1) Dipartimento di Chimica, Università degli Studi di Firenze 2) Istituto dei Sistemi Complessi - CNR, Firenze 3) Dipartimento di Fisica, Università degli Studi di Firenze, 4) The Lewis Magnetism Laboratory, School of Chemistry, The University of Manchester (literal)
Titolo
  • Hyperfine Interactions And Spin Dynamics In The Cr7fe(Ii) Antiferromagnetic Wheel Probed By Moessbauer Spectroscopy (literal)
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