Single-ion and molecular contributions to the zero-field splitting in an iron(III)-oxo dimer studied by single crystal W-band EPR

Heerdt, P.; Stefan, M.; Goovaerts, E.; Caneschi, Andréa; Cornia, Andrea

doi:10.1016/j.jmr.2005.10.016

Cited by 36 publications

(45 citation statements)

References 45 publications

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“…In a very similar compound was found Dð1Þ ' 6 K [12] and we expect, in the present case, analogous values for the anisotropy constant. Consequently, the anisotropy splitting for the S ¼ 2 multiplet is one order of magnitude smaller than the magnetic separations (about 6 K) due to the 5 T external field.…”

Section: Spin Statessupporting

confidence: 89%

Magnetic anisotropy and spin fluctuations in the paramagnetic dimer : Mössbauer spectroscopy and ab initio calculations

Cianchi

Giallo

Moretti

et al. 2008

Journal of Magnetism and Magnetic Materials

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Section: Spin Statessupporting

confidence: 89%

Magnetic anisotropy and spin fluctuations in the paramagnetic dimer : Mössbauer spectroscopy and ab initio calculations

Cianchi

Giallo

Moretti

et al. 2008

Journal of Magnetism and Magnetic Materials

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“…[17,36], the lacking of the spin-spin contribution could not account for the big difference between the computed and the experimental single ion anisotropy values and the simulation protocol employed leads to a slight underestimation of the single ions contribution. However, the computed anisotropic exchange parameters result in fairly good agreement with the experimental ones both in sign and magnitude [19]. In Table 1 we reported the computed values for anisotropic exchange anisotropy tensors.…”

Section: X-ray Structuresupporting

confidence: 68%

“…This class of SMMs represents one of the most investigated systems and represents a valuable ensemble of good candidates for future device fabrication. An experimental EPR study of Fe 2 shows that this system behaves as two S = 5/2 iron ions whose spectrum is well described by the Spin Hamiltonian [19]. The leading interaction is the isotropic interaction J 12 whose value is 15.4 cm −1 .…”

Section: Introductionmentioning

confidence: 98%

The Role of Anisotropic Exchange in Single Molecule Magnets: A CASSCF/NEVPT2 Study of the Fe4 SMM Building Block [Fe2(OCH3)2(dbm)4] Dimer

Lunghi

Totti

2016

Inorganics

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Abstract:The rationalisation of single molecule magnets' (SMMs) magnetic properties by quantum mechanical approaches represents a major task in the field of the Molecular Magnetism. The fundamental interpretative key of molecular magnetism is the phenomenological Spin Hamiltonian and the understanding of the role of its different terms by electronic structure calculations is expected to steer the rational design of new and more performing SMMs. This paper deals with the ab initio calculation of isotropic and anisotropic exchange contributions in the Fe(III) dimer [Fe 2 (OCH 3 ) 2 (dbm) 4 ]. This system represents the building block of one of the most studied Single Molecule Magnets ([Fe 4 RC(CH 2 O) 3 ) 2 (dpm) 6 ] where R can be an aliphatic chain or a phenyl group just to name the most common functionalization groups) and its relatively reduced size allows the use of a high computational level of theory. Calculations were performed using CASSCF and NEVPT2 approaches on the X-ray geometry as assessment of the computational protocol, which has then be used to evinced the importance of the outer coordination shell nature through organic ligand modelization. Magneto-structural correlations as function of internal degrees of freedom for isotropic and anisotropic exchange contributions are also presented, outlining, for the first time, the extremely rapidly changing nature of the anisotropic exchange coupling.

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“…The ori- entation of the local anisotropy centers for which we get the best agreement with experiments (D M = -0⋅28 K) corresponds to θ ~ 82°. 35,36 As with Mn 12 Ac, we find that the laboratory frame we have chosen is very close to molecular axis in all the cases. In case of Fe 8 cluster, the D 2 symmetry commutes with the Hamiltonian in (10) and allows for a non-zero E M term.…”

Section: Methodsmentioning

confidence: 79%

“…The relativistic used the single-ion anisotropy values quoted in the literature for the magnetic ions in similar ligand environments. [33][34][35][36] The local ion axis referred to as x, y and z and the laboratory axis denoted by X, Y and Z are shown in figure 7. The laboratory frame can be arbitrarily chosen since, while computing the molecular anisotropy, we diagonalize the anisotropy tensor and obtain the anisotropy values along the three principal directions.…”

Section: Methodsmentioning

confidence: 99%

Computing magnetic anisotropy constants of single molecule magnets

et al. 2009

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We present here a theoretical approach to compute the molecular magnetic anisotropy parameters, D M and E M for single molecule magnets in any given spin eigenstate of exchange spin Hamiltonian. We first describe a hybrid constant M S -valence bond (VB) technique of solving spin Hamiltonians employing full spatial and spin symmetry adaptation and we illustrate this technique by solving the exchange Hamiltonian of the Cu 6 Fe 8 system. Treating the anisotropy Hamiltonian as perturbation, we compute the D M and E M values for various eigenstates of the exchange Hamiltonian. Since, the dipolar contribution to the magnetic anisotropy is negligibly small, we calculate the molecular anisotropy from the single-ion anisotropies of the metal centers. We have studied the variation of D M and E M by rotating the single-ion anisotropies in the case of Mn 12 Ac and Fe 8 SMMs in ground and few low-lying excited states of the exchange Hamiltonian. In both the systems, we find that the molecular anisotropy changes drastically when the single-ion anisotropies are rotated. While in Mn 12 Ac SMM D M values depend strongly on the spin of the eigenstate, it is almost independent of the spin of the eigenstate in Fe 8 SMM. We also find that the D M value is almost insensitive to the orientation of the anisotropy of the core Mn(IV) ions. The dependence of D M on the energy gap between the ground and the excited states in both the systems has also been studied by using different sets of exchange constants.

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Single-ion and molecular contributions to the zero-field splitting in an iron(III)-oxo dimer studied by single crystal W-band EPR

Cited by 36 publications

References 45 publications

Magnetic anisotropy and spin fluctuations in the paramagnetic dimer : Mössbauer spectroscopy and ab initio calculations

Magnetic anisotropy and spin fluctuations in the paramagnetic dimer : Mössbauer spectroscopy and ab initio calculations

The Role of Anisotropic Exchange in Single Molecule Magnets: A CASSCF/NEVPT2 Study of the Fe4 SMM Building Block [Fe2(OCH3)2(dbm)4] Dimer

Computing magnetic anisotropy constants of single molecule magnets

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