Andrea Caneschi

Large clusters of metal ions: The transition from molecular to bulk magnets

Clusters of metal ions are a class of compounds actively investigated for their magnetic properties, which should gradually change from those of simple paramagnets to those of bulk magnets. However, their interest lies in a number of different disciplines: chemistry, which seeks new synthetic strategies to make larger and larger clusters in a controlled manner; physics, which can test the validity of quantum mechanical approaches at the nanometer scale; and biology, which can use them as models of biomineralization of magnetic particles.

Magnetic Anisotropy and Spin‐Parity Effect Along the Series of Lanthanide Complexes with DOTA

Spotting trends: Upon going from Tb(III) to Yb(III) centers in the complexes of the DOTA(4-) ligand, a reorientation of the easy axis of magnetization from perpendicular to parallel to the Ln-O bond of the apical water molecule is experimentally observed and theoretically predicted (SMM=single-molecule magnet). Only ions with an odd number of electrons show slow relaxation of the magnetization.

Magnetic Anisotropy of Dysprosium(III) in a Low-Symmetry Environment: A Theoretical and Experimental Investigation

A mixed theoretical and experimental approach was used to determine the local magnetic anisotropy of the dysprosium(III) ion in a low-symmetry environment. The susceptibility tensor of the monomeric species having the formula [Dy(hfac)(3)(NIT-C(6)H(4)-OEt)(2)], which contains nitronyl nitroxide (NIT-R) radicals, was determined at various temperatures through angle-resolved magnetometry. These results are in agreement with ab initio calculations performed using the complete active space self-consistent field (CASSCF) method, validating the predictive power of this theoretical approach for complex systems containing rare-earth ions, even in low-symmetry environments. Susceptibility measurements performed with the applied field along the easy axis eventually permitted a detailed analysis of the temperature and field dependence of the magnetization, providing evidence that the Dy ion transmits an antiferromagnetic interaction between radicals but that the Dy-radical interaction is ferromagnetic.

The molecular approach to nanoscale magnetism

Abstract Molecular clusters of paramagnetic metal ions have been widely investigated as model for magnetism at the nanoscale, especially for quantum effects like the tunneling of the magnetic moment. We present here some recent results obtained on derivatives of the well-known Mn12 cluster, especially on the half-integer spin compounds. The role of the transverse anisotropy in the dynamics of the magnetization is here elucidated through the comparison of the tunneling rate of the magnetization in two Fe8 cluster compounds, which differ only in the transverse anisotropy. Local dipolar fields and nuclear hyperfine fields have also revealed to strongly affect the relaxation in the pure tunneling regime and recent experiment has allowed to determine the intrinsic linewidth of the tunneling resonance. The transverse field dependence of the relaxation rate of Fe8 has revealed oscillations that are analog to the topological constructive–destructive interference of the spin phase (Berry phase) and we review here some very recent results. The magnetic behavior of antiferromagnetic ring-shaped clusters is also discussed for their potential interest as models for antiferromagnetic particles. Some recent results obtained by other chemists in the synthesis of large spin clusters are also reviewed.

Low-Energy Magnetic Excitations of the Mn 12 -Acetate Spin Cluster Observed by Neutron Scattering

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Finite-size effects in single chain magnets: an experimental and theoretical study.

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Antiferromagnetic Coupling in a Gadolinium(III) Semiquinonato Complex

-acetate by inelastic neutron scattering and diffraction. We separated the energy levels corresponding to the splitting of the lowest

X‐Ray Detected Magnetic Hysteresis of Thermally Evaporated Terbium Double‐Decker Oriented Films

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2,2′-Bipyrimidine (bipym)-bridged dinuclear complexes. Part 4. Synthesis, crystal structure and magnetic properties of [CO2(H2O)8(bipym)][NO3]4, [CO2(H2O)8(bipym)][SO4]2·2H2O and [CO2(bipym)3(NCS)4]

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Strong magneto-chiral dichroism in a paramagnetic molecular helix observed by hard X-rays

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