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Titolo:
Single-ion versus dipolar origin of the magnetic anisotropy in iron(III)-oxo clusters: A case study
Autore:
Abbati, GL; Brunel, LC; Casalta, H; Cornia, A; Fabretti, AC; Gatteschi, D; Hassan, AK; Jansen, AGM; Maniero, AL; Pardi, L; Paulsen, C;
Indirizzi:
Univ Florence, Dipartimento Chim, I-50144 Florence, Italy Univ Florence Florence Italy I-50144 mento Chim, I-50144 Florence, Italy Univ Modena & Reggio Emilia, Dipartimento Chim, I-41100 Modena, Italy UnivModena & Reggio Emilia Modena Italy I-41100 , I-41100 Modena, Italy Natl High Magnet Field Lab, Tallahassee, FL 32310 USA Natl High Magnet Field Lab Tallahassee FL USA 32310 ahassee, FL 32310 USA Inst Max Von Laue Paul Langevin, CNRS, F-38042 Grenoble, France Inst Max Von Laue Paul Langevin Grenoble France F-38042 Grenoble, France FKF, MPI, Grenoble High Magnet Field Lab, F-38042 Grenoble, France FKF Grenoble France F-38042 h Magnet Field Lab, F-38042 Grenoble, France CNRS, F-38042 Grenoble, France CNRS Grenoble France F-38042CNRS, F-38042 Grenoble, France CNR, Ist Fis Atom & Mol, I-56127 Pisa, Italy CNR Pisa Italy I-56127CNR, Ist Fis Atom & Mol, I-56127 Pisa, Italy CNRS, Ctr Rech Tres Basses Temp, F-38042 Grenoble, France CNRS Grenoble France F-38042 Tres Basses Temp, F-38042 Grenoble, France
Titolo Testata:
CHEMISTRY-A EUROPEAN JOURNAL
fascicolo: 8, volume: 7, anno: 2001,
pagine: 1796 - 1807
SICI:
0947-6539(20010417)7:8<1796:SVDOOT>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
HIGH-SPIN MOLECULES; FERROMAGNETIC EXCHANGE INTERACTIONS; RAY CRYSTALLOGRAPHIC STRUCTURE; INELASTIC NEUTRON-SCATTERING; FIELD TORQUE MAGNETOMETRY; ENTRAPPING ALKALINE IONS; HOST-GUEST INTERACTIONS; FREQUENCY EPR-SPECTRA; GROUND-STATE; TERT-BUTYLGALLIUM;
Keywords:
cluster compounds; EPR spectroscopy; gallium; iron; magnetic properties;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
87
Recensione:
Indirizzi per estratti:
Indirizzo: Gatteschi, D Univ Florence, Dipartimento Chim, Via Maragliano 77, I-50144 Florence, Italy Univ Florence Via Maragliano 77 Florence Italy I-50144 Italy
Citazione:
G.L. Abbati et al., "Single-ion versus dipolar origin of the magnetic anisotropy in iron(III)-oxo clusters: A case study", CHEM-EUR J, 7(8), 2001, pp. 1796-1807

Abstract

A multitechnique approach has allowed the first experimental determinationof single-ion anisotropies in a large iron(m)-oxo cluster, namely [Na-Fe-6(OCH3)(12)(pmdbm)(6)]ClO4 (1) in which Hpmdbm = 1,3-bis(4-methoxyphenyl)- 1,3-propanedione. High-frequency EPR (HF-EPR), bulk susceptibility measurements, and high-field cantilever torque magnetometry (HF-CTM) have been applied to iron-doped samples of an isomorphous hexagallium(III) cluster [NaGa6(OCH3)(12)-(pmdbm)(6)]ClO4, whose synthesis and X-ray structure are also presented. HF-EPR at 240 GHz and susceptibility data have shown that the iron(III) ions have a hard-axis type anisotropy with D-Fe = 0.43(1) cm(-1) and E-Fe = 0.066(3) cm(-1) in the zero-field splitting (ZFS) Hamiltonian H = D-Fe[S-z(2) - S(S + 1)/3] + E-Fe[S-x(2) - S-y(2)]. HF-CTM at 0.4 K has then been used to establish the orientation of the ZFS tensors with respect to theunique molecular axis of the cluster. Z. The hard magnetic axes of the iron(III) ions are found to be almost perpendicular to Z, so that the anisotropic components projected onto Z are negative, D-Fe(ZZ) = - 0.164(1) cm(-1),Due to the dominant antiferromagnetic coupling, a negative D-Fe(ZZ) value determines a hard-axis molecular anisotropy in 1 as experimentally observed. By adding point-dipolar interactions between iron(III) spins, the calculated ZFS parameter of the triplet state, D-1 = 4,70(9) cm(-1), is in excellent agreement with that determined by inelastic neutron scattering experiments at 2K, D-1 = 4.57(2) cm(-1) Iron-doped samples of a structurally relatedcompound, the dimer [Ga-2(OCH3)(2)(dbm)(4)] (Hdbm = dibenzoylmethone), have also been investigated by HF-EPR at 525 GHz, The single-ion anisotropy isof the hard-axis type as well. but the D-Fe parameter is significantly larger [D-Fe = 0.770(3) cm(-1),E-Fe = 0.090(3) cm(-1)]. We conclude that, although the ZFS tensors depend very unpredictably on the coordination environment of the metal ions, single-ion terms can contribute significantly to themagnetic anisotropy of iron(III)-oxo clusters, which are currently investigated as single-molecule magnets.

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Documento generato il 24/09/20 alle ore 05:11:55