1,721,090 research outputs found
Single-molecule Magnets Based on Iron(III) Oxo Clusters
No full textPolynuclear compounds of magnetic transition metal ions are attracting large interest after the discovery that their magnetisation may relax very slowly at low temperature. Since their behaviour is similar to that of bulk magnets they may be called single molecule magnets. Here we review the magnetic properties of iron(III) clusters showing such features which may be interesting for future applications, as well as strategies for designing new molecules with increased performances
New Experimental Techniques for Magnetic Anisotropy in Molecular Materials
No full textMagnetic anisotropy is a very important property in magnetochemistry. Its knowledge allows us to obtain a fundamental understanding of the electronic structure of both simple paramagnetic species and of magnetically coupled systems. The difficulties associated with its experimental determination have so far limited its investigation. Recently new experimental techniques using superconducting quantum interference devices (SQUID) and micro-SQUID arrays as well as cantilever torque magnetometry have drastically reduced the size of the crystals needed for the measurements, thus opening new perspectives. We will briefly review here these techniques, with the aim to advertise their use in the chemical community
Answer to the comment of Chudnovsky: On the square-root time relaxation in molecular nanomagnets
No full text1 pageInternational audienceAnswer to the comment of E. Chudnovsky concerning the following papers: (1) N.V. Prokofév, P.C.E. Stamp, Phys. Rev. Lett.80, 5794 (1998). (2) W. Wernsdorfer, T. Ohm, C. Sangregorio, R. Sessoli, D. Mailly, C. Paulsen, Phys. Rev. Lett. 82, 3903 (1999)
Organizing and Addressing Magnetic Molecules
No full textMagnetic molecules ranging from simple organic radicals to single-molecule magnets (SMMs) are intensively investigated for their potential applications in molecule-based information storage and processing. The goal of this Article is to review recent achievements in the organization of magnetic molecules on surfaces and in their individual probing and manipulation. We stress that the inherent fragility and redox sensitivity of most SMM complexes, combined with the noninnocent role played by the substrate, ask for a careful evaluation of the structural andelectronic properties of deposited molecules going beyond routine methods for surface analysis. Detailed magnetic information can be directly obtained using X-ray magnetic circular dichroism or newly emerging scanning probe techniques with magnetic detection capabilities
Magnetism of Large Iron-Oxo Clusters
No full textThe role of large iron-ore clusters in chemistry, material science, and fundamental physics is briefly reviewed. Examples of clusters with nuclearity ranging from 6 to 19 are reported as well as their magnetic properties. Relevant topics, such as the role of spin topology and spin frustration in antiferromagnetically coupled systems and the observation of superparamagnetic like behaviour and molecular hysteresis, are discussed. The use of strong magnetic fields in the characterization of magnetic clusters is emphasized and a theoretical approach for the rationalization of the magnetic properties of clusters is briefly reported
Nonadiabatic Landau Zener Tunneling and Quantum Phase Interference in Fe-8 Molecular Nanomagnets
No full textThe Landau-Zener method allows to measure very small tunnel splittings Δ in mol. clusters Fe8. The obsd. oscillations of Δ as a function of the magnetic field applied along the hard anisotropy axis are explained in terms of topol. quantum interference of two tunnel paths of opposite windings. Studies of the temp. dependence of the Landau-Zener transition rate P gives access to the topol. quantum interference between excited spin levels. The influence of nuclear spins is demonstrated by comparing P of the std. Fe8 sample with two isotopically substituted samples. The need of a generalized Landau-Zener transition rate theory is shown
Chemical Strategies and Characterization Tools for the Organization of Single Molecule Magnets on Surfaces
No full textAddressing individual bistable magnetic molecules, known as Single Molecule Magnets (SMMs), is a fascinating goal at the borderline between molecular magnetism and spin electronics. This tutorial review focuses on the first step towards single-molecule experiments, namely the organization of SMMs on surfaces. Both preparation and characterization of surface-supported SMMs prove to be quite demanding and a multidisciplinary approach is necessary, which is described here using selected examples. We first illustrate the chemical strategies devised to assemble SMMs and to control their orientation on surfaces. Then, we present characterization tools, which have been selected on the basis of their relevance to address specific points, i.e. the chemical composition of the deposited SMM films, the organization of the molecules on the surface, the intramolecular arrangement of the spins, the magnetic anisotropy of SMMs, and eventually the dynamics of their magnetization on surfaces. Particular attention is devoted to techniques exploiting synchrotron light
Nonadiabatic Landau–Zener Tunneling in Fe8 Molecular Nanomagnets
No full textThe Landau-Zener method allows to measure very small tunnel splittings ∆ in molecular clusters Fe8. The observed oscillations of ∆ as a function of the magnetic field applied along the hard anisotropy axis are explained in terms of topological quantum interference of two tunnel paths of opposite windings. Studies of the temperature dependence of the Landau-Zener transition rate P gives access to the topological quantum interference between excited spin levels. The influence of nuclear spins is demonstrated by comparing P of the standard Fe8 sample with two isotopically substituted samples. The need of a generalised Landau-Zener transition rate theory is shown
Magnetism from the Molecular to the Nanoscale
No full textA review on nanoscale molecule-based magnetic materials composed of exchange-coupled metal ions. The review covers simple oligonuclear species, antiferromagnetic rings and Single Molecule Magnets. Finally, it describes the most recent developments in one-dimensional chain-like systems, including the exotic spin dynamics exhibited by Single Chain Magnets
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