Philippe Sainctavit | Université Paris III - Sorbonne Nouvelle (original) (raw)
Papers by Philippe Sainctavit
Springer Proceedings in Physics, 2010
... These are in general polynuclear coordination compounds of paramagnetic metal ions held R. Se... 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 ...
Monatshefte f�r Chemie / Chemical Monthly, 2003
Molecular chemistry allows to synthesize new magnetic systems with controlled properties such as ... more Molecular chemistry allows to synthesize new magnetic systems with controlled properties such as size, magnetization or anisotropy. The theoretical study of the magnetic properties of small molecules (from 2 to 10 metallic cations per molecule) predicts that the magnetization at saturation of each ion does not reach the expected value for uncoupled ions when the magnetic interaction is antiferromagnetic. The quantum origin of this effect is due to the linear combination of several spin states building the wave function of the ground state and clusters of finite size and of finite spin value exhibit this property. When single crystals are available, spin densities on each atom can be experimentally given by Polarized Neutron Diffraction (PND) experiments. In the case of bimetallic MnCu powdered samples, we will show that X-ray Magnetic Circular Dichroism (XMCD) spectroscopy can be used to follow the evolution of the spin distribution on the Mn II and Cu II sites when passing from a dinuclear MnCu unit to a one dimensional (MnCu) n compound.
Journal of Magnetism and Magnetic Materials
Magnetic anisotropies and crystallographic structures of cobalt-iron nanospinels obtained with th... more Magnetic anisotropies and crystallographic structures of cobalt-iron nanospinels obtained with the co-precipitation synthesis process are revealed using X-ray Absorption Spectroscopy and X-ray Magnetic Circular Dichroism. The chemical process allows to obtain nanoparticles of various sizes and chemical composition, but it is the site symmetry environment of Co 2+ that is found to be the crucial parameter that governs the magnetic anisotropies of the nanospinels. The distribution of Co 2+ among the crystallographic sites of the structure is directly linked to the temperature of the synthesis process. In parallel, the results also revealed that a superficial rich shell of iron is formed for the iron-cobalt nanospinels stable in acidic medium leading to chemically inhomogeneous nanoparticles.
Chemistry - A European Journal
Journal of Physics-condensed Matter, 1996
We present full multiple-scattering calculations at the aluminium K edge that we compare with exp... 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
A simple procedure based on anion exchange was employed for the enantiomeric resolution of the ex... 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 Mat... more 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 ...
Journal of Physics: Conference Series
We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO3 single cry... more We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO3 single crystal in temperature range from 5 to 300 K and external magnetic field of 17 T. The response consists of pre-edge (at 7712 eV) and bi-polar peak (up at 7727, down at 7731 eV) with amplitudes, respectively, less than 10-3 and 10-2 of the Co K-edge jump. Using the sum rule the orbital magnetic moment of 4p Co is evaluated. Its temperature dependence reaches a maximum of (2.7 ± 0.9) x 10-3 µB at 120 K, following the trend for the total magnetic moment on the Co obtained from the superconducting quantum interference device measurements. However, on warming from 25 to 120 K, the orbital magnetic moment of the 4p Co doubles while total magnetic moment of Co increases 10 times. First principle calculations are in order to relate the Co K-edge XMCD results to the orbital and spin moment of 3d Co.
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 6, 2016
In a proof-of-principle study, a soluble macrocyclic single-molecule magnet (SMM) containing a Cu... 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.
MRS Proceedings, 1991
ABSTRACTWe present an application of multiple scattering theory with “muffin-tin” potentials to t... 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.
Journal of Physics: …, 1995
... Printed in the UK Linear x-ray dichroism of cadmium sulphide with wurtzite and zincblende str... 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. ...
We have checked the XMCD sum rules through an analytical calculation of Cu 2+ L 2,3 edges in octa... 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.
Ferrihydrite is an important iron oxyhydroxide for earth and environmental sciences, biology, and... more Ferrihydrite is an important iron oxyhydroxide for earth and environmental sciences, biology, and technology. Nevertheless, its mineral structure remains a matter of debate. The stumbling block is whether a significant amount of tetrahedrally coordinated iron is present. Here we present the first X-ray magnetic circular dichroïsm (XMCD) measurements performed on a well characterized synthetic sample of 6-line ferrihydrite, at both K and L 2,3 energy edges of iron. XMCD results demonstrate unambiguously the presence of tetrahedrally coordinated Fe(III) in the mineral structure, in quantities compatible with the latest extended X-ray absorption fine structure (EXAFS) analyses suggesting a concentration of 20-30%. Moreover, we find an antiferromagnetic coupling between tetrahedral and octahedral sublattices, with the octahedral sublattice parallel to the external magnetic field.
The Journal of Physical Chemistry C
Small (Weinheim an der Bergstrasse, Germany), 2018
The complexation between 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (NaP... 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.
Springer Proceedings in Physics, 2010
... These are in general polynuclear coordination compounds of paramagnetic metal ions held R. Se... 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 ...
Monatshefte f�r Chemie / Chemical Monthly, 2003
Molecular chemistry allows to synthesize new magnetic systems with controlled properties such as ... more Molecular chemistry allows to synthesize new magnetic systems with controlled properties such as size, magnetization or anisotropy. The theoretical study of the magnetic properties of small molecules (from 2 to 10 metallic cations per molecule) predicts that the magnetization at saturation of each ion does not reach the expected value for uncoupled ions when the magnetic interaction is antiferromagnetic. The quantum origin of this effect is due to the linear combination of several spin states building the wave function of the ground state and clusters of finite size and of finite spin value exhibit this property. When single crystals are available, spin densities on each atom can be experimentally given by Polarized Neutron Diffraction (PND) experiments. In the case of bimetallic MnCu powdered samples, we will show that X-ray Magnetic Circular Dichroism (XMCD) spectroscopy can be used to follow the evolution of the spin distribution on the Mn II and Cu II sites when passing from a dinuclear MnCu unit to a one dimensional (MnCu) n compound.
Journal of Magnetism and Magnetic Materials
Magnetic anisotropies and crystallographic structures of cobalt-iron nanospinels obtained with th... more Magnetic anisotropies and crystallographic structures of cobalt-iron nanospinels obtained with the co-precipitation synthesis process are revealed using X-ray Absorption Spectroscopy and X-ray Magnetic Circular Dichroism. The chemical process allows to obtain nanoparticles of various sizes and chemical composition, but it is the site symmetry environment of Co 2+ that is found to be the crucial parameter that governs the magnetic anisotropies of the nanospinels. The distribution of Co 2+ among the crystallographic sites of the structure is directly linked to the temperature of the synthesis process. In parallel, the results also revealed that a superficial rich shell of iron is formed for the iron-cobalt nanospinels stable in acidic medium leading to chemically inhomogeneous nanoparticles.
Chemistry - A European Journal
Journal of Physics-condensed Matter, 1996
We present full multiple-scattering calculations at the aluminium K edge that we compare with exp... 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
A simple procedure based on anion exchange was employed for the enantiomeric resolution of the ex... 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 Mat... more 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 ...
Journal of Physics: Conference Series
We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO3 single cry... more We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO3 single crystal in temperature range from 5 to 300 K and external magnetic field of 17 T. The response consists of pre-edge (at 7712 eV) and bi-polar peak (up at 7727, down at 7731 eV) with amplitudes, respectively, less than 10-3 and 10-2 of the Co K-edge jump. Using the sum rule the orbital magnetic moment of 4p Co is evaluated. Its temperature dependence reaches a maximum of (2.7 ± 0.9) x 10-3 µB at 120 K, following the trend for the total magnetic moment on the Co obtained from the superconducting quantum interference device measurements. However, on warming from 25 to 120 K, the orbital magnetic moment of the 4p Co doubles while total magnetic moment of Co increases 10 times. First principle calculations are in order to relate the Co K-edge XMCD results to the orbital and spin moment of 3d Co.
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 6, 2016
In a proof-of-principle study, a soluble macrocyclic single-molecule magnet (SMM) containing a Cu... 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.
MRS Proceedings, 1991
ABSTRACTWe present an application of multiple scattering theory with “muffin-tin” potentials to t... 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.
Journal of Physics: …, 1995
... Printed in the UK Linear x-ray dichroism of cadmium sulphide with wurtzite and zincblende str... 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. ...
We have checked the XMCD sum rules through an analytical calculation of Cu 2+ L 2,3 edges in octa... 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.
Ferrihydrite is an important iron oxyhydroxide for earth and environmental sciences, biology, and... more Ferrihydrite is an important iron oxyhydroxide for earth and environmental sciences, biology, and technology. Nevertheless, its mineral structure remains a matter of debate. The stumbling block is whether a significant amount of tetrahedrally coordinated iron is present. Here we present the first X-ray magnetic circular dichroïsm (XMCD) measurements performed on a well characterized synthetic sample of 6-line ferrihydrite, at both K and L 2,3 energy edges of iron. XMCD results demonstrate unambiguously the presence of tetrahedrally coordinated Fe(III) in the mineral structure, in quantities compatible with the latest extended X-ray absorption fine structure (EXAFS) analyses suggesting a concentration of 20-30%. Moreover, we find an antiferromagnetic coupling between tetrahedral and octahedral sublattices, with the octahedral sublattice parallel to the external magnetic field.
The Journal of Physical Chemistry C
Small (Weinheim an der Bergstrasse, Germany), 2018
The complexation between 2-ureido-4[1H]-pyrimidinone (UPy) and 2,7-diamido-1,8-naphthyridine (NaP... 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.