Tuning Anisotropy Barriers in a Family of Tetrairon(III) Single-Molecule Magnets with an<i>S</i>= 5 Ground State

Accorsi, Stefania; Barra, Anne‐Laure; Caneschi, Andréa; Chastanet, Guillaume; Cornia, Andrea; Fabretti, Antonio C.; Gatteschi, Dante; Mortalò, Cecilia; Olivieri, E.; Parenti, Francesca; Rosa, Patrick; Sessoli, Roberta; Sorace, Lorenzo; Wernsdorfer, Wolfgang; Zobbi, Laura

doi:10.1021/ja0576381

Cited by 201 publications

(336 citation statements)

References 67 publications

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“…These levels were identified by a preliminary analysis of the field dependent energy pattern using anisotropy parameters from previous works. conclusion, which fully supports previous studies, 36,40,42 implies that the hard axis (z) of each D Fe(i) tensor is normal to the corresponding Cr-Fe(i) direction, with no symmetryimposed restriction on the angle β between z and Z. However, γ can have only two possible values, 0 or 90°, depending on whether y or x is found along Cr-Fe(i).…”

Section: Fig 7 (Color Online) Arrangement Of Single-ion Anisotropy Tsupporting

confidence: 89%

“…We have thus synthesized the new complex [Fe 3 Cr(L) 2 (dpm) 6 ] (1) and found that it has crystallographically-imposed trigonal (D 3 ) symmetry, like its tetrairon(III) analogue. 23,40 We present here a singlecrystal W-band EPR study on 1, which has provided the first spectroscopic determination of high-order transverse anisotropy in a threefold symmetric SMM. The results allow us to draw a detailed picture of the relation between GSA and MSA, highlighting the role of non-collinear single-ion anisotropy tensors.…”

Section: Introductionmentioning

confidence: 99%

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Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet

et al. 2013

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W-band ( ν ≅ 94 GHz) Electron Paramagnetic Resonance (EPR) spectroscopy was used for a singlecrystal study on a star-shaped Fe 3 Cr Single Molecule Magnet (SMM) with crystallographically-imposed trigonal symmetry. The high resolution and sensitivity accessible with W-band EPR allowed us to determine accurately the axial zero-field splitting terms for the ground (S=6) and first two excited states (S = 5 and S = 4). Further, spectra recorded by applying the magnetic field perpendicular to the trigonal axis showed a π/6 angular modulation. This behavior is a signature of the presence of trigonal transverse magnetic anisotropy terms which were spectroscopically determined for the first time in a SMM. Such an in-plane anisotropy could only be justified by dropping the so-called "giant spin approach" (GSA), and by considering a complete multi-spin approach (MSA). From a detailed analysis of experimental data with the two models, it emerged that the observed trigonal anisotropy directly reflects the structural features of the cluster, i.e. the relative orientation of single-ion anisotropy tensors and the angular modulation of single-ion anisotropy components in the hard plane of the cluster. Finally, since high-order transverse anisotropy is pivotal in determining the spin dynamics in the quantum tunneling regime, we have compared the angular dependence of the tunnel splitting predicted by the two models upon application of a transverse field (Berry Phase Interference).

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Section: Fig 7 (Color Online) Arrangement Of Single-ion Anisotropy Tsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet

et al. 2013

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“…Envisioning the use of our hybrid junctions as a superconducting molecular transistor, we present here preliminary results obtained from coupling an individual Fe 4 single-molecule magnet 27 (SMM) to superconducting leads (schematically shown in Fig. 1(d)).…”

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confidence: 99%

Superconducting molybdenum-rhenium electrodes for single-molecule transport studies

Gaudenzi

Island

Bruijckere

et al. 2015

Applied Physics Letters

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We demonstrate that electronic transport through single molecules or molecular ensembles, commonly based on gold (Au) electrodes, can be extended to superconducting electrodes by combining gold with molybdenum-rhenium (MoRe). This combination induces proximity-effect superconductivity in the gold to temperatures of at least 4.6 Kelvin and magnetic fields of 6 Tesla, improving on previously reported aluminum based superconducting nanojunctions. As a proof of concept, we show three-terminal superconductive transport measurements through an individual Fe 4 single-molecule magnet.Recent advances in nanostructure fabrication have made possible to couple superconductivity (SC) with confined systems of electrons. From this interaction, interesting phenomena like Andreev reflections 1 and YuShiba-Rusinov states 2-5 emerge where SC can be used alternatively as a probe to characterize the mesoscopic system 6 or as a tool to influence it 7-9 . When the confined system is an individual molecule or a nanocrystal, additional internal degrees of freedom like spin and vibrations are predicted to have an effect on the Cooper pair transport. For instance, supercurrent can be employed as a probe for isotropic and anisotropic spinful molecules 10,11 . So far, only a handful of studies have investigated superconducting transport through individual molecules. Two recent examples are scanning tunneling microscopy studies using lead 9,12 and two-terminal devices using tungsten 13 . However, due to the absence of a gate, these studies are limited to the off-resonant transport regime and a single fixed charge state. Further studies, involving a combination of resonant transport and SC, are based on electromigrated gold break junctions 14 . These junctions are equipped with a gate electrode in close proximity to the molecule thereby forming a single-molecule transistor. Due to the difficulty of electromigrating materials other than gold, SC is typically induced by proximity to a superconducting material like aluminum 15 . The small superconducting gap of aluminum (∆ ≈ 0.18 meV, T c ≈ 1.2 K, B c ≈ 10 mT), however, limits the range of operation in magnetic field and temperature. In particular, the conditions for attaining the intermediate coupling transport regime (Γ ∼ ∆ ∼ k B T K ) restrict the range of molecular couplings Γ and Kondo energy scales k B T K . As a consequence limited room is left for the investigation of this intriguing regime where single-electron and many-body physics are directly competing 7,8,16,17 . a) These authors contributed equally.

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“…1a), where acac is acetyl acetonate or 2,4-pentanedionate, and Br-mp 3− is the anion of 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol (Br-mpH 3 ) [24]. This molecule was chosen because the zero-field splitting is such that the ground state magnetic resonance transition is close to zero field in our spectrometer, in contrast to the case of other thoroughly investigated and chemically similar Fe 4 clusters [25]. In this molecule the central iron(III) spin is coupled antiferromagnetically to the peripheral iron(III) spins resulting in an S = 5 molecular spin ground state.…”

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confidence: 99%

Direct Observation of Quantum Coherence in Single-Molecule Magnets

et al. 2008

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Direct evidence of quantum coherence in a single-molecule magnet in frozen solution is reported with coherence times as long as T2 = 630 ± 30 ns. We can strongly increase the coherence time by modifying the matrix in which the single-molecule magnets are embedded. The electron spins are coupled to the proton nuclear spins of both the molecule itself and interestingly, also to those of the solvent. The clear observation of Rabi oscillations indicates that we can manipulate the spin coherently, an essential prerequisite for performing quantum computations.PACS numbers: 75.30.Gw, 75.50.Xx, The key concept in quantum information processing is that a quantum bit (qubit) may be not just 0 or 1, as in ordinary computer bits, but an arbitrary superposition of 0 and 1. This means that any two-level system, that can be put into a superposition state, is a qubit candidate [1]. The required superposition state is created by electromagnetic radiation pulses with a frequency corresponding to the energy splitting between the two levels ( Fig. 1c). The contribution of each of the two levels to the superposition state has a cyclic dependence on the pulse length, leading to so-called Rabi oscillations [1]. The observation of such oscillations is a proof-of-principle for the viability of performing quantum computations with a particular system. Quantum computers will probably not be realized from single atoms but will most likely utilize solid state devices, such as superconducting junctions, semiconductor structures, or molecular magnets [1,2]. For these large systems the quantum coherence decays fast, which drastically shortens the time available for quantum computation. Molecular magnets have been considered as qubits because they can be easily organized into large-scale ordered arrays by surface self-assembly [? ], and because they possess excited electronic-spin states required for two-qubit gate operations [5,6]. Single-molecule magnets (SMMs) are exchange-coupled clusters with highspin ground states [3]. The Ising-type anisotropy creates an energy barrier toward magnetization relaxation [ Fig. 1(b)], and many fascinating quantum phenomena have been observed in these systems, such as quantum tunnelling of the magnetization and quantum phase interference [3]. The large splitting of the two lowest states of SMMs in zero field (in principle) allows performing coherent spin-manipulations without external magnetic field, which simplifies any practical implementation. SMMs have also been proposed for the implementation of Grover's algorithm [2] allowing numbers between 0 and 2 2S−2 to be stored in a single molecule.The long coherence time is a crucial first step towards successful implementation of SMMs as qubits [1]. Therefore, recent years have seen a great deal of activity in trying to determine the quantum coherence times in SMMs, which was estimated to be of the order of 10 ns [7,8,9,10]. In several cases, energy gaps between superposition states have been reported that are larger than the expected decoherence energy scale [...

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Tuning Anisotropy Barriers in a Family of Tetrairon(III) Single-Molecule Magnets with anS= 5 Ground State

Cited by 201 publications

References 67 publications

Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet

Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet

Superconducting molybdenum-rhenium electrodes for single-molecule transport studies

Direct Observation of Quantum Coherence in Single-Molecule Magnets

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