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Dive into the research topics where Boris Tsukerblat is active.

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Featured researches published by Boris Tsukerblat.


Nature | 2008

Quantum oscillations in a molecular magnet

Sylvain Bertaina; Serge Gambarelli; Tamoghna Mitra; Boris Tsukerblat; Achim Müller; B. Barbara

The term ‘molecular magnet’ generally refers to a molecular entity containing several magnetic ions whose coupled spins generate a collective spin, S (ref. 1). Such complex multi-spin systems provide attractive targets for the study of quantum effects at the mesoscopic scale. In these molecules, the large energy barriers between collective spin states can be crossed by thermal activation or quantum tunnelling, depending on the temperature or an applied magnetic field. There is the hope that these mesoscopic spin states can be harnessed for the realization of quantum bits—‘qubits’, the basic building blocks of a quantum computer—based on molecular magnets. But strong decoherence must be overcome if the envisaged applications are to become practical. Here we report the observation and analysis of Rabi oscillations (quantum oscillations resulting from the coherent absorption and emission of photons driven by an electromagnetic wave) of a molecular magnet in a hybrid system, in which discrete and well-separated magnetic clusters are embedded in a self-organized non-magnetic environment. Each cluster contains 15 antiferromagnetically coupled S = 1/2 spins, leading to an S = 1/2 collective ground state. When this system is placed into a resonant cavity, the microwave field induces oscillatory transitions between the ground and excited collective spin states, indicative of long-lived quantum coherence. The present observation of quantum oscillations suggests that low-dimension self-organized qubit networks having coherence times of the order of 100 μs (at liquid helium temperatures) are a realistic prospect.


Journal of the American Chemical Society | 2008

A Highly Anisotropic Cobalt(II)-Based Single-Chain Magnet: Exploration of Spin Canting in an Antiferromagnetic Array

Andrei V. Palii; Oleg S. Reu; Sergei M. Ostrovsky; Sophia I. Klokishner; Boris Tsukerblat; Zhong-Ming Sun; Jiang-Gao Mao; Andrey V. Prosvirin; Hanhua Zhao; Kim R. Dunbar

In this article we report for the first time experimental details concerning the synthesis and full characterization (including the single-crystal X-ray structure) of the spin-canted zigzag-chain compound [Co(H2L)(H2O)]infinity [L = 4-Me-C6H4-CH2N(CPO3H2)2], which contains antiferromagnetically coupled, highly magnetically anisotropic Co(II) ions with unquenched orbital angular momenta, and we also propose a new model to explain the single-chain magnet behavior of this compound. The model takes into account (1) the tetragonal crystal field and the spin-orbit interaction acting on each Co(II) ion, (2) the antiferromagnetic Heisenberg exchange between neighboring Co(II) ions, and (3) the tilting of the tetragonal axes of the neighboring Co units in the zigzag structure. We show that the tilting of the anisotropy axes gives rise to spin canting and consequently to a nonvanishing magnetization for the compound. In the case of a strong tetragonal field that stabilizes the orbital doublet of Co(II), the effective pseudo-spin-1/2 Hamiltonian describing the interaction between the Co ions in their ground Kramers doublet states is shown to be of the Ising type. An analytical expression for the static magnetic susceptibility of the infinite spin-canted chain is obtained. The model provides an excellent fit to the experimental data on both the static and dynamic magnetic properties of the chain.


Journal of The Electrochemical Society | 2008

Luminescent Properties of Ca-α-SiAlON : Eu2 + Phosphors Synthesized by Gas-Pressured Sintering

Jeong Ho Ryu; Youn-Gon Park; Hyong Sik Won; Sang-Hyun Kim; Hideo Suzuki; Jong Myeon Lee; Chulsoo Yoon; Mihail Nazarov; Do Young Noh; Boris Tsukerblat

Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, Ca-α-SiAlON:Eu 2+ based yellow and orange oxynitride phosphors with compositions of Ca 0.485 Eu 0.015 Si 9.2 Al 2.8 O 1.8 N 14.2 and Ca 0.94 Eu 0.06 Si 9 Al 3 ON 15 were prepared using the gas-pressured sintering method. The crystallinity and particle morphology of the prepared phosphors were characterized. The temperature dependence of photoluminescence properties was investigated from 25 to 150°C. The Stokes shift and zero-phonon line was calculated mathematically and estimated from the spectral data. The prepared Ca-α-SiAlON:Eu 2+ phosphors showed superior thermal quenching properties compared to commercially used YAG:Ce 3+ phosphors. In addition, the activation energies (ΔE) for thermal quenching of the prepared Ca-α-SiAlON:Eu 2+ phosphors were determined by Arrhenius fitting.


International Reviews in Physical Chemistry | 2010

Magnetic exchange between metal ions with unquenched orbital angular momenta: basic concepts and relevance to molecular magnetism

Andrei V. Palii; Boris Tsukerblat; Juan M. Clemente-Juan; Eugenio Coronado

This review article is a first attempt to give a systematic and comprehensive description (in the framework of the unified theoretical approach) of the exchange interactions in polynuclear systems based on orbitally degenerate metal ions in the context of their relevance to the modern molecular magnetism. Interest in these systems is related to the fundamental problems of magnetism and at the same time steered by a number of impressive potential applications of molecular magnets, like high-density memory storage units, nanoscale qubits, spintronics and photoswitchable devices. In the presence of orbital degeneracy, the conventional spin Hamiltonian (Heisenberg–Dirac–van Vleck model) becomes inapplicable even as an approximation. The central component of this review article constitutes the concept of orbitally-dependent exchange interaction between metal ions possessing unquenched orbital angular momenta. We present a rigorous procedure of derivation of the kinetic exchange Hamiltonian for a pair of orbitally degenerate transition metal ions that is expressed in terms of the orbital matrices and spin operators. The microscopic background reveals the interrelations between the parameters of the Hamiltonian and the internal parameters of the system including all relevant transfer integrals and fundamental intracenter interactions. The developed formalism integrated with the irreducible tensor operator (ITO) technique makes it possible to describe the exchange coupling and all relevant interactions (crystal fields, spin–orbit (SO) and Zeeman couplings) in terms of the ITOs of the full spherical group, and in this way to develop anunified and efficient computational tool. The orbitally-dependent exchange was shown to lead to an anomalously strong magnetic anisotropy that can be considered as a main physical manifestation of the unquenched orbital angular momentum in metal clusters of orbitally-degenerate ions. The theoretical background is illustrated by the following applications. The magnetic properties of the binuclear face-shared unit [Ti2Cl9]3− in Cs3Ti2Cl9 are discussed with the emphasis on the observed magnetic anisotropy and on the non-trivial symmetry properties of the exchange Hamiltonian. The major electronic factors controlling the magnetic anisotropy in Co(II) pairs are discussed. The degree of the exchange anisotropy was shown to depend on the strength of the cubic crystal field, on the relative efficiency of the electron transfer pathways between unfilled d-shells and SO coupling. Provided strong SO coupling, the effective Hamiltonian was projected onto the subspace of low-lying Kramers doublets and similarly a pseudo-spin-1/2 Hamiltonian was derived. The described procedure allows to establish the interrelation between idem parameters of the system and the parameters of the pseudo-spin-1/2 Hamiltonian. Pseudo-spin-1/2 approach is illustrated by the study of the inelastic neutron scattering spectra and magnetic susceptibility of polyoxometalates encapsulating Co(II) clusters: Keggin derivative K8[Co2(D2O)(W11O39)] · nD2O, [Co4(H2O)2(PW9O34)2]10− and [Co3W(D2O)2(CoW9O34)2]12− clusters. In the consideration of the cyanide-bridged Mn(III)–CN–Mn(II) pair, it was demonstrated that under certain conditions the orbitally-dependent exchange is able to produce a barrier for the reversal of magnetisation. This seems to be instructive for the controlled design of cyano-based single molecule magnets with high-blocking temperatures.


Journal of Chemical Physics | 2003

Orbitally dependent magnetic coupling between cobalt(II) ions: The problem of the magnetic anisotropy

A.V. Palii; Boris Tsukerblat; Eugenio Coronado; Juan M. Clemente-Juan; J.J. Borrás-Almenar

A comprehensive theoretical study of the magnetic exchange between Co2+ ions is reported. Using the microscopic background we deduce the general Hamiltonian for a corner shared bioctahedral system involving kinetic exchange, spin–orbit coupling, and low-symmetry local crystal field. This Hamiltonian acting within the orbitally degenerate ground manifold (4T1g)A⊗(4T1g)B of the cobalt pair is expressed in terms of orbital and spin operators. The treatment of the Hamiltonian is performed with the use of the irreducible tensor operator technique. We elucidate the major electronic factors controlling the magnetic anisotropy in the Co(II) pairs. The degree of the exchange anisotropy is shown to depend on the strength of the cubic crystal field and on the relative efficiency of two kinds of electron transfer pathways (e–e and t2–t2) contributing to the kinetic exchange. An unusual role of spin–orbit interaction is revealed. This interaction tends to reduce the anisotropy caused by the orbitally dependent exchang...


Journal of Chemical Physics | 2006

Low temperature EPR spectra of the mesoscopic cluster V15: The role of antisymmetric exchange

Boris Tsukerblat; Alex Tarantul; Achim Müller

The low temperature EPR spectra of the unique nanometer-scale molecular magnet V(15) are analyzed within the three-spin model preserving trigonal symmetry. The Hamiltonian includes isotropic and antisymmetric (AS) exchange interactions introduced by Dzyaloshinsky (Zh. Eksp. Teor. Fiz. 32, 1547 (1957) [Sov. Phys. JETP 5, 1259 (1957)]) and [Moria Phys. Rev. 120, 91 (1960)]. With the aid of pseudoangular momentum representation the exact selection rules for the EPR transitions are deduced. AS exchange in the frustrated triangular system gives rise to a first order zero-field splitting of two low lying spin doublets and to a second order splitting of the excited quadruplet. This leads to a peculiar series of strong intramultiplet transitions and weak intermultiplet transitions. We show that the intramultiplet transitions are allowed only when the vector of the AS exchange is normal to the plane of vanadium triangle, but the series of weak intermultiplet transitions are a consequence of the in-plane part of the AS exchange. We have revealed a special temperature dependence of the EPR pattern with a peculiar shape of the full spectrum. Experimental data on high-frequency EPR of V15 at ultralow temperature are discussed.


Journal of Chemical Theory and Computation | 2005

Control of the Barrier in Cyanide Based Single Molecule Magnets Mn(III)2Mn(II)3: Theoretical Analysis

Boris Tsukerblat; Andrew Palii; Sergei M. Ostrovsky; Sergei V. Kunitsky; Sophia I. Klokishner; Kim R. Dunbar

The aim of this communication is to probe the possibility of increasing the barrier for reversal of magnetization in the family of new cyano-bridged pentanuclear Mn(III)2Mn(II)3 clusters in which single molecule magnet behavior has been recently discovered. In this context, we analyze the global magnetic anisotropy arising from the unquenched orbital angular momenta of ground terms (3)T1(t2(4)) of the two apical Mn(III) ions. The model takes into account the trigonal component of the crystal field, spin-orbit interaction in (3)T1(t2(4)), and an isotropic exchange interaction between Mn(III) and Mn(II) ions. The height of the barrier is shown to be sensitive to the change of the trigonal field stabilizing orbital doublet (3)E, which carries the first-order orbital magnetic contribution and enhances with an increase of the trigonal field. This result is expected to be useful for the more rational design of new cyano-bridged SMMs with high blocking temperatures.


Journal of Physical Chemistry A | 2009

Highly Anisotropic Exchange Interactions in a Trigonal Bipyramidal Cyanide-Bridged NiII3OSIII2 Cluster

Andrei V. Palii; Oleg S. Reu; Sergei M. Ostrovsky; Sophia I. Klokishner; Boris Tsukerblat; Matthew G. Hilfiger; Michael Shatruk; Andrey V. Prosvirin; Kim R. Dunbar

This article is a part of our efforts to control the magnetic anisotropy in cyanide-based exchange-coupled systems with the eventual goal to obtain single-molecule magnets with higher blocking temperatures. We give the theoretical interpretation of the magnetic properties of the new pentanuclear complex {[Ni(II)(tmphen)(2)](3)[Os(III)(CN)(6)](2)} x 6 CH(3)CN (Ni(II)(3)Os(III)(2) cluster). Because the system contains the heavy Os(III) ions, spin-orbit coupling considerably exceeds the contributions from the low-symmetry crystal field and exchange coupling. The magnetic properties of the Ni(II)(3)Os(III)(2) cluster are described in the framework of a highly anisotropic pseudo-spin Hamiltonian that corresponds to the limit of strong spin-orbital coupling and takes into account the complex molecular structure. The model provides a good fit to the experimental data and allows the conclusion that the trigonal axis of the bipyramidal Ni(II)(3)Os(III)(2) cluster is a hard axis of magnetization. This explains the fact that in contrast with the isostructural trigonal bipyramidal Mn(III)(2)Mn(II)(3) cluster, the Ni(II)(3)Os(III)(2) system does not exhibit the single-molecule magnetic behavior.


Inorganic Chemistry | 2009

High-Nuclearity Mixed-Valence Clusters and Mixed-Valence Chains: General Approach to the Calculation of the Energy Levels and Bulk Magnetic Properties

Juan M. Clemente-Juan; J.J. Borrás-Almenar; Eugenio Coronado; Andrew Palii; Boris Tsukerblat

A general approach to the problem of electron delocalization in the high-nuclearity mixed-valence (MV) clusters containing an arbitrary number of localized spins and itinerant electrons is developed. Along with the double exchange, we consider the isotropic magnetic exchange between the localized electrons as well as the Coulomb intercenter repulsion. As distinguished from the previous approaches dealing with the MV systems in which itinerant electrons are delocalized over all constituent metal sites, here, we consider a more common case of systems exhibiting partial delocalization and containing several delocalized domains. Taking full advantage of the powerful angular momentum technique, we were able to derive closed form analytical expressions for the matrix elements of the full Hamiltonian. These expressions provide an efficient tool for treating complex mixed-valence systems, because they contain only products of 6j-symbols (that appear while treating the delocalized parts) and 9j-symbols (exchange interactions in localized parts) and do not contain high-order recoupling coefficients and 3j-symbols that essentially constrained all previous theories of mixed valency. The approach developed here is accompanied by an efficient computational procedure that allows us to calculate the bulk thermodynamic properties (magnetic susceptibility, magnetization, and magnetic specific heat) of high-nuclearity MV clusters. Finally, this approach has been used to discuss the magnetic properties of the octanuclear MV cluster [Fe(8)(mu(4)-O)(4)(4-Cl-pz)(12)Cl(4)](-) and the diphthalocyanine chains [YPc(2)].CH(2)Cl(2) and [ScPc(2)].CH(2)Cl(2) composed of MV dimers interacting through the magnetic exchange and Coulomb repulsion.


ChemPhysChem | 2012

Electric field control of the spin state in mixed-valence magnetic molecules.

Cristian Bosch-Serrano; Juan M. Clemente-Juan; Eugenio Coronado; Alejandro Gaita-Ariño; Andrew Palii; Boris Tsukerblat

Multiferroic molecules for spintronics: In a many-electron mixed-valence dimer with dominant double exchange, as compared with antiferromagnetic superexchange, the electric field is shown to induce a spin crossover from the ferromagnetic spin state to the antiferromagnetic one. This leads to a sharp decrease in the magnetic moment of the molecule and a simultaneous stepwise increase in the electric dipole (see figure).

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Alex Tarantul

Ben-Gurion University of the Negev

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S. M. Aldoshin

Russian Academy of Sciences

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Do Young Noh

Gwangju Institute of Science and Technology

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Mihail Nazarov

Gwangju Institute of Science and Technology

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