... These are in general polynuclear coordination compounds of paramagnetic metal ions held R. Sessoli (B) Laboratory for Molecular Magnetism, Department of Chemistry and INSTM RU, University of Florence, 50019 Sesto Fiorentino, Italy... more
... These are in general polynuclear coordination compounds of paramagnetic metal ions held R. Sessoli (B) Laboratory for Molecular Magnetism, Department of Chemistry and INSTM RU, University of Florence, 50019 Sesto Fiorentino, Italy e-mail: roberta.sessoli@unifi.it ...
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We present full multiple-scattering calculations at the aluminium K edge that we compare with experiments for four crystalline silicates and oxide minerals. In the different minerals aluminium atoms are either fourfold or sixfold... more
We present full multiple-scattering calculations at the aluminium K edge that we compare with experiments for four crystalline silicates and oxide minerals. In the different minerals aluminium atoms are either fourfold or sixfold coordinated to oxygen atoms in Al sites that are poorly symmetric. The calculations are based on different choices of one-electron potentials according to aluminium coordinations and crystallographic
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A simple procedure based on anion exchange was employed for the enantiomeric resolution of the extended metal atom chain (EMAC) [Co3(dpa)4(MeCN)2]. Use of the chiral anion [As2(tartrate)2](NBu4)2, (Λ-1 or Δ-1), resulted in the selective... more
A simple procedure based on anion exchange was employed for the enantiomeric resolution of the extended metal atom chain (EMAC) [Co3(dpa)4(MeCN)2]. Use of the chiral anion [As2(tartrate)2](NBu4)2, (Λ-1 or Δ-1), resulted in the selective crystallization of the EMAC enantiomers as diastereomeric [ΔCo3(dpa)4(MeCN)2][NBu4]2[Λ-As2(tartarte)2]2, (Δ-2) and [ΛCo3(dpa)4(MeCN)2][NBu4]2[Δ-As2(tartarte)2]2 (Λ-2), respectively, in the P4212 space group, whereas a racemic mixture of 1 yielded [Co3(dpa)4(MeCN)2][As2(tartrate)2]·2MeCN (rac-3), which crystallized in the C2/c space group. The local electronic and magnetic structure of the EMAC enantiomers was studied, exploiting a variety of dichroisms in single crystals [1]. A strong linear dichroism at the Co K-edge was observed in the orthoaxial configuration, whereas it vanished in the axial orientation, thus spectroscopically confirming the D4 crystal symmetry. Compounds Δ-2 and Λ-2 are shown to be enantiopure materials as evidenced by mirror-im...
Page 1. XMCD FOR THE INVESTIGATION OF SINGLE MOLECULE MAGNETS BASED SELF-ASSEMBLED MONOLAYERS Matteo MANNINI,a Philippe SAINCTAVIT,b Chiara DANIELI,c Francesco PINEIDER,a Christophe CARTIER ...
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In a proof-of-principle study, a soluble macrocyclic single-molecule magnet (SMM) containing a Cu(II)3 Tb(III) magnetic core was covalently grafted onto small gold nanoparticles pre-functionalised with carboxylate-terminated tethers. A... more
In a proof-of-principle study, a soluble macrocyclic single-molecule magnet (SMM) containing a Cu(II)3 Tb(III) magnetic core was covalently grafted onto small gold nanoparticles pre-functionalised with carboxylate-terminated tethers. A modified microemulsion method allowed production of the small and monodisperse nanoparticles (approximately 3.5 nm in diameter) for the chemisorption of a large amount of intact macrocyclic complexes in the hybrid system.
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ABSTRACTWe present an application of multiple scattering theory with “muffin-tin” potentials to the calculation of X-ray absorption cross section. We have measured and calculated the K-edge spectra of atoms in compounds with zincblende... more
ABSTRACTWe present an application of multiple scattering theory with “muffin-tin” potentials to the calculation of X-ray absorption cross section. We have measured and calculated the K-edge spectra of atoms in compounds with zincblende structure : SiC, ZnS. We show that some spectral features can be precisely related to the local environnement around the absorbing atom.
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... Printed in the UK Linear x-ray dichroism of cadmium sulphide with wurtzite and zincblende structures C Levelutt, Ph Sainctavit, A Ramos and J Petiau Laboratoire de Min6ralogie Cristallographie, CNRS URA9, Universites Paris 6 et 7.4... more
... Printed in the UK Linear x-ray dichroism of cadmium sulphide with wurtzite and zincblende structures C Levelutt, Ph Sainctavit, A Ramos and J Petiau Laboratoire de Min6ralogie Cristallographie, CNRS URA9, Universites Paris 6 et 7.4 Place Jussieu, 75252 Paris adex OS. ...
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We have checked the XMCD sum rules through an analytical calculation of Cu 2+ L 2,3 edges in octahedral symmetry. It is found that XMCD sum rules are fully satisfied in the framework of the crystal field multiplet approach resulting from... more
We have checked the XMCD sum rules through an analytical calculation of Cu 2+ L 2,3 edges in octahedral symmetry. It is found that XMCD sum rules are fully satisfied in the framework of the crystal field multiplet approach resulting from the very general arguments developed in their derivations by B.T. Thole and collaborators. Analytical expressions for the orbital magnetic moment 〈 L z 〉, the spin magnetic moment 〈 S z 〉 and the magnetic dipole term 〈 T z 〉 are obtained as functions of crystal field strength and spin–orbit couplings. The nullity of 〈 T z 〉 is specially examined through group theory considerations, and it is found that at low temperature the 〈 T z 〉 contribution can be much larger than the 〈 S z 〉 contribution in the spin sum rule. The case of Ti 3+ in octahedral symmetry is also considered and it is found that, even for no spin–orbit coupling, 〈 T z 〉 can be non-zero.
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The complexation between 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (NaPy) is used to promote the mild chemisorption of a UPy-functionalized terbium(III) double decker system on a silicon surface. The adopted... more
The complexation between 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (NaPy) is used to promote the mild chemisorption of a UPy-functionalized terbium(III) double decker system on a silicon surface. The adopted strategy allows the single-molecule magnet behavior of the system to be maintained unaltered on the surface.
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We demonstrate that Fe4 molecules can be deposited on gold by thermal sublimation in ultra-high vacuum with retention of single molecule magnet behavior. A magnetic hysteresis comparable to that found in bulk samples is indeed observed... more
We demonstrate that Fe4 molecules can be deposited on gold by thermal sublimation in ultra-high vacuum with retention of single molecule magnet behavior. A magnetic hysteresis comparable to that found in bulk samples is indeed observed when a submonolayer film is studied by X-ray magnetic circular dichroism. Scanning tunneling microscopy evidences that Fe4 molecules are assembled in a two-dimensional lattice with short-range hexagonal order and coexist with a smaller contaminant. The presence of intact Fe4 molecules and the retention of their bistable magnetic behavior on the gold surface are supported by density functional theory calculations.
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Thin films of an iron(II) complex with a photochromic diarylethene-based ligand and featuring a spin-crossover behaviour have been grown by sublimation in ultra-high vacuum on highly oriented pyrolytic graphite and...
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A simple procedure based on anion exchange was employed for the enantiomeric resolution of the extended metal atom chain (EMAC) [Co(dpa)(MeCN)]. Use of the chiral salt (NBu)[As(tartrate)], (Λ- or Δ-), resulted in the selective... more
A simple procedure based on anion exchange was employed for the enantiomeric resolution of the extended metal atom chain (EMAC) [Co(dpa)(MeCN)]. Use of the chiral salt (NBu)[As(tartrate)], (Λ- or Δ-), resulted in the selective crystallization of the EMAC enantiomers as [Δ-Co(dpa)(MeCN)](NBu)[Λ-As(tartarte)], (Δ-) and [Λ-Co(dpa)(MeCN)](NBu)[Δ-As(tartrate)] (Λ-), respectively, in the 422 space group, whereas a racemic mixture of yielded [Co(dpa)(MeCN)][As(tartrate)]·2MeCN (-), which crystallized in the 2/ space group. The local electronic and magnetic structure of the EMAC enantiomers was studied, exploiting a variety of dichroisms in single crystals. A strong linear dichroism at the Co K-edge was observed in the orthoaxial configuration, whereas it vanished in the axial orientation, thus spectroscopically confirming the crystal symmetry. Compounds Δ- and Λ- are shown to be enantiopure materials as evidenced by mirror-image natural circular dichroism spectra in the UV/vis in solution ...
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X-ray magnetic circular dichroism is measured at the Fe K pre-edge in yttrium iron garnet using two different procedures that allow reducing the intrinsic broadening due to the 1s corehole lifetime. First, deconvolution of XMCD data... more
X-ray magnetic circular dichroism is measured at the Fe K pre-edge in yttrium iron garnet using two different procedures that allow reducing the intrinsic broadening due to the 1s corehole lifetime. First, deconvolution of XMCD data measured in total fluorescence yield (TFY) with an extremely high signal-to-noise ratio enables a factor of 2.4 to be gained in the XMCD intensity. Ligand field multiplet calculations performed with different values of intrinsic broadening show that deconvolving such high quality XMCD data is similar to reducing the lifetime broadening from a 1s corehole to a 2p corehole. Second, MCD is measured by resonant inelastic x-ray scattering spectroscopy as a function of incident energy and emission energy. Selection of a fixed emission energy, instead of using the TFY, allows enhancing the MCD intensity up to a factor of ∼4.7. However, this significantly changes the spectral shape of the XMCD signal, which cannot be interpreted any more as an absorption spectrum.
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The magnetic properties of some single molecule magnets (SMM) on surfaces can be strongly modified by the molecular packing in nanometric films/aggregates or by interactions with the substrate, which affect the molecular orientation and... more
The magnetic properties of some single molecule magnets (SMM) on surfaces can be strongly modified by the molecular packing in nanometric films/aggregates or by interactions with the substrate, which affect the molecular orientation and geometry. Detailed investigations of the magnetism of thin SMM films and nanostructures are necessary for the development of spin-based molecular devices, however this task is challenged by the limited sensitivity of laboratory-based magnetometric techniques and often requires access to synchrotron light sources to perform surface sensitive X-ray magnetic circular dichroism (XMCD) investigations. Here we show that low-temperature magnetic force microscopy is an alternative powerful laboratory tool able to extract the field dependence of the magnetization and to identify areas of in-plane and perpendicular magnetic anisotropy in microarrays of the SMM terbium(III) bis-phthalocyaninato (TbPc2) neutral complex grown as nanosized films on SiO2 and peryle...
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Cantilever torque magnetometry is used to elucidate the orientation of magnetic molecules in thin films. The technique allows depth-resolved investigations by intercalating a layer of anisotropic magnetic molecules in a film of its... more
Cantilever torque magnetometry is used to elucidate the orientation of magnetic molecules in thin films. The technique allows depth-resolved investigations by intercalating a layer of anisotropic magnetic molecules in a film of its isotropic analogues. The proof-of-concept is here demonstrated with the single-molecule magnet TbPc2 evidencing also an exceptional long range templating effect on substrates coated by the organic molecule perylene-3,4,9,10-tetracarboxylic dianhydride.
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We present an x-ray magnetic circular dichroism study performed at the U M4,5 edges on UFe2, a ferromagnet with almost itinerant 5f electrons. The analysis of the branching ratio of the U M4,5 edges confirms the fact that the occupation... more
We present an x-ray magnetic circular dichroism study performed at the U M4,5 edges on UFe2, a ferromagnet with almost itinerant 5f electrons. The analysis of the branching ratio of the U M4,5 edges confirms the fact that the occupation number of the 5f states in UFe2 is lower than in other compounds where the f electrons are more localized.
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Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest-and more attractive-systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic... more
Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest-and more attractive-systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [Co(II)(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination-without nanoparticle aggregation and without complex dissociation-of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blockin...
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Prussian blue analogues have attracted great attention because they have interesting magnetic properties with high critical temperatures up to 350 K. A spontaneous stabilization method in water has permitted to obtain crystalline... more
Prussian blue analogues have attracted great attention because they have interesting magnetic properties with high critical temperatures up to 350 K. A spontaneous stabilization method in water has permitted to obtain crystalline nanoparticles of these networks, which makes possible in a control manner the epitaxial growth of a second network of the same family.[1] This result has been confirmed by a chemical mapping (EELS technique) and by images (HRTEM).[1] Typically, a first subnetwork core Cs x M II [M III (CN) 6 ] y is surrounded by a second sub network Cs x M' II [M III (CN) 6 ] y of the same family. The ac susceptibility measurement of the nanoparticles has showed a superparamagnetic or spin glass like behavior depending on the particle size and the dilution of the sample. The obtained core shell evidenced a synergy between the magnetic properties of the two subnetworks. X-Ray Magnetic Circular Dichroism (XMCD) is a X-ray absorption spectroscopy dedicated to the measureme...
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We have presented the Multiple Scattering Theory applied to the calculation of X-ray absorption spectra. We have specially outlined that in this technique the contributions from the potential and from the structure could be separated. The... more
We have presented the Multiple Scattering Theory applied to the calculation of X-ray absorption spectra. We have specially outlined that in this technique the contributions from the potential and from the structure could be separated. The essence of the theory resides in solving equations of continuity that have a compact expression in the case of “muffin-tin” potentials. The construction of
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This chapter is divided into three main parts. In the first section we outline the reasons why low temperature measurements are necessary in x-ray absorption spectroscopy and more specifically in x-ray magnetic circular dichroism.... more
This chapter is divided into three main parts. In the first section we outline the reasons why low temperature measurements are necessary in x-ray absorption spectroscopy and more specifically in x-ray magnetic circular dichroism. Emphasis is given to the different ways temperature can yield modifications on the experimental spectra. In the second section, a description of the principles of normal