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Chiesa A, Santini P, Garlatti E, Luis F, Carretta S. Molecular nanomagnets: a viable path toward quantum information processing? Rep Prog Phys 2024; 87:034501. [PMID: 38314645 DOI: 10.1088/1361-6633/ad1f81] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 01/17/2024] [Indexed: 02/06/2024]
Abstract
Molecular nanomagnets (MNMs), molecules containing interacting spins, have been a playground for quantum mechanics. They are characterized by many accessible low-energy levels that can be exploited to store and process quantum information. This naturally opens the possibility of using them as qudits, thus enlarging the tools of quantum logic with respect to qubit-based architectures. These additional degrees of freedom recently prompted the proposal for encoding qubits with embedded quantum error correction (QEC) in single molecules. QEC is the holy grail of quantum computing and this qudit approach could circumvent the large overhead of physical qubits typical of standard multi-qubit codes. Another important strength of the molecular approach is the extremely high degree of control achieved in preparing complex supramolecular structures where individual qudits are linked preserving their individual properties and coherence. This is particularly relevant for building quantum simulators, controllable systems able to mimic the dynamics of other quantum objects. The use of MNMs for quantum information processing is a rapidly evolving field which still requires to be fully experimentally explored. The key issues to be settled are related to scaling up the number of qudits/qubits and their individual addressing. Several promising possibilities are being intensively explored, ranging from the use of single-molecule transistors or superconducting devices to optical readout techniques. Moreover, new tools from chemistry could be also at hand, like the chiral-induced spin selectivity. In this paper, we will review the present status of this interdisciplinary research field, discuss the open challenges and envisioned solution paths which could finally unleash the very large potential of molecular spins for quantum technologies.
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Affiliation(s)
- A Chiesa
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- INFN-Sezione di Milano-Bicocca, Gruppo Collegato di Parma, 43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
| | - P Santini
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- INFN-Sezione di Milano-Bicocca, Gruppo Collegato di Parma, 43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
| | - E Garlatti
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- INFN-Sezione di Milano-Bicocca, Gruppo Collegato di Parma, 43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
| | - F Luis
- Instituto de Nanociencia y Materiales de Aragon (INMA), CSIC, Universidad de Zaragoza, Zaragoza, Spain
- Departamento de Fısica de la Materia Condensada, Universidad de Zaragoza, Zaragoza, Spain
| | - S Carretta
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- INFN-Sezione di Milano-Bicocca, Gruppo Collegato di Parma, 43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
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2
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Garlatti E, Albino A, Chicco S, Nguyen VHA, Santanni F, Paolasini L, Mazzoli C, Caciuffo R, Totti F, Santini P, Sessoli R, Lunghi A, Carretta S. The critical role of ultra-low-energy vibrations in the relaxation dynamics of molecular qubits. Nat Commun 2023; 14:1653. [PMID: 36964152 PMCID: PMC10039010 DOI: 10.1038/s41467-023-36852-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 02/15/2023] [Indexed: 03/26/2023] Open
Abstract
Improving the performance of molecular qubits is a fundamental milestone towards unleashing the power of molecular magnetism in the second quantum revolution. Taming spin relaxation and decoherence due to vibrations is crucial to reach this milestone, but this is hindered by our lack of understanding on the nature of vibrations and their coupling to spins. Here we propose a synergistic approach to study a prototypical molecular qubit. It combines inelastic X-ray scattering to measure phonon dispersions along the main symmetry directions of the crystal and spin dynamics simulations based on DFT. We show that the canonical Debye picture of lattice dynamics breaks down and that intra-molecular vibrations with very-low energies of 1-2 meV are largely responsible for spin relaxation up to ambient temperature. We identify the origin of these modes, thus providing a rationale for improving spin coherence. The power and flexibility of our approach open new avenues for the investigation of magnetic molecules with the potential of removing roadblocks toward their use in quantum devices.
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Affiliation(s)
- E Garlatti
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, I-43124, Parma, Italy
- INFN, Sezione di Milano-Bicocca, gruppo collegato di Parma, I-43124, Parma, Italy
| | - A Albino
- Dipartimento di Chimica 'Ugo Schiff', Università Degli Studi di Firenze and UdR Firenze, INSTM, I-50019, Sesto Fiorentino, Italy
| | - S Chicco
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, I-43124, Parma, Italy
| | - V H A Nguyen
- School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, Ireland
| | - F Santanni
- Dipartimento di Chimica 'Ugo Schiff', Università Degli Studi di Firenze and UdR Firenze, INSTM, I-50019, Sesto Fiorentino, Italy
| | - L Paolasini
- ESRF - The European Synchrotron Radiation Facility, F-38043, Grenoble, Cedex 09, France
| | - C Mazzoli
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - R Caciuffo
- INFN, Sezione di Genova, I-16146, Genova, Italy
| | - F Totti
- Dipartimento di Chimica 'Ugo Schiff', Università Degli Studi di Firenze and UdR Firenze, INSTM, I-50019, Sesto Fiorentino, Italy
| | - P Santini
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, I-43124, Parma, Italy
- INFN, Sezione di Milano-Bicocca, gruppo collegato di Parma, I-43124, Parma, Italy
| | - R Sessoli
- Dipartimento di Chimica 'Ugo Schiff', Università Degli Studi di Firenze and UdR Firenze, INSTM, I-50019, Sesto Fiorentino, Italy.
| | - A Lunghi
- School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, Ireland.
| | - S Carretta
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, I-43124, Parma, Italy.
- INFN, Sezione di Milano-Bicocca, gruppo collegato di Parma, I-43124, Parma, Italy.
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3
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Abstract
We pinpoint the key ingredients ruling decoherence in multispin clusters, and we engineer the system Hamiltonian to design optimal molecules embedding quantum error correction. These are antiferromagnetically coupled systems with competing exchange interactions, characterized by many low-energy states in which decoherence is dramatically suppressed and does not increase with the system size. This feature allows us to derive optimized code words, enhancing the power of the quantum error correction code by orders of magnitude. We demonstrate this by a complete simulation of the system dynamics, including the effect of decoherence driven by a nuclear spin bath and the full sequence of pulses to implement error correction and logical gates between protected states.
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Affiliation(s)
- A. Chiesa
- Università
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, I-43124 Parma, Italy
- Gruppo
Collegato di Parma, INFN−Sezione
di Milano-Bicocca, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - F. Petiziol
- Institut
für Theoretische Physik, Technische
Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
| | - M. Chizzini
- Università
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, I-43124 Parma, Italy
- Gruppo
Collegato di Parma, INFN−Sezione
di Milano-Bicocca, 43124 Parma, Italy
| | - P. Santini
- Università
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, I-43124 Parma, Italy
- Gruppo
Collegato di Parma, INFN−Sezione
di Milano-Bicocca, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - S. Carretta
- Università
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, I-43124 Parma, Italy
- Gruppo
Collegato di Parma, INFN−Sezione
di Milano-Bicocca, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
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4
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Chiesa A, Chizzini M, Garlatti E, Salvadori E, Tacchino F, Santini P, Tavernelli I, Bittl R, Chiesa M, Sessoli R, Carretta S. Assessing the Nature of Chiral-Induced Spin Selectivity by Magnetic Resonance. J Phys Chem Lett 2021; 12:6341-6347. [PMID: 34228926 PMCID: PMC8397348 DOI: 10.1021/acs.jpclett.1c01447] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 06/21/2021] [Indexed: 05/20/2023]
Abstract
Understanding chiral-induced spin selectivity (CISS), resulting from charge transport through helical systems, has recently inspired many experimental and theoretical efforts but is still the object of intense debate. In order to assess the nature of CISS, we propose to focus on electron-transfer processes occurring at the single-molecule level. We design simple magnetic resonance experiments, exploiting a qubit as a highly sensitive and coherent magnetic sensor, to provide clear signatures of the acceptor polarization. Moreover, we show that information could even be obtained from time-resolved electron paramagnetic resonance experiments on a randomly oriented solution of molecules. The proposed experiments will unveil the role of chiral linkers in electron transfer and could also be exploited for quantum computing applications.
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Affiliation(s)
- A. Chiesa
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - M. Chizzini
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
| | - E. Garlatti
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - E. Salvadori
- Dipartimento
di Chimica & NIS Centre, Università
di Torino, Via P. Giuria
7, I-10125 Torino, Italy
| | - F. Tacchino
- IBM
Quantum, IBM Research—Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - P. Santini
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - I. Tavernelli
- IBM
Quantum, IBM Research—Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - R. Bittl
- Freie
Universität Berlin, Fachbereich Physik, Berlin Joint EPR Lab, Arnimallee 14, D-14195 Berlin, Germany
| | - M. Chiesa
- Dipartimento
di Chimica & NIS Centre, Università
di Torino, Via P. Giuria
7, I-10125 Torino, Italy
| | - R. Sessoli
- Dipartimento
di Chimica “Ugo Schiff” & INSTM, Università Degli Studi di Firenze, I-50019 Sesto Fiorentino, Italy
| | - S. Carretta
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
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5
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Chiesa A, Carretta S, Santini P, Amoretti G, Pavarini E. Erratum: Many-Body Models for Molecular Nanomagnets [Phys. Rev. Lett. 110, 157204 (2013)]. Phys Rev Lett 2021; 126:069901. [PMID: 33635720 DOI: 10.1103/physrevlett.126.069901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Indexed: 06/12/2023]
Abstract
This corrects the article DOI: 10.1103/PhysRevLett.110.157204.
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6
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Chiesa A, Macaluso E, Petiziol F, Wimberger S, Santini P, Carretta S. Molecular Nanomagnets as Qubits with Embedded Quantum-Error Correction. J Phys Chem Lett 2020; 11:8610-8615. [PMID: 32936660 DOI: 10.1063/9.0000166] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 02/02/2021] [Indexed: 05/24/2023]
Abstract
We show that molecular nanomagnets have a potential advantage in the crucial rush toward quantum computers. Indeed, the sizable number of accessible low-energy states of these systems can be exploited to define qubits with embedded quantum error correction. We derive the scheme to achieve this crucial objective and the corresponding sequence of microwave/radiofrequency pulses needed for the error correction procedure. The effectiveness of our approach is shown already with a minimal S = 3/2 unit corresponding to an existing molecule, and the scaling to larger spin systems is quantitatively analyzed.
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Affiliation(s)
- A Chiesa
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
| | - E Macaluso
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
| | - F Petiziol
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
| | - S Wimberger
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- INFN, Sezione di Milano Bicocca, Gruppo Collegato di Parma, Parma, Italy
| | - P Santini
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
| | - S Carretta
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR Parma, INSTM, I-43124 Parma, Italy
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7
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Chiesa A, Macaluso E, Petiziol F, Wimberger S, Santini P, Carretta S. Molecular Nanomagnets as Qubits with Embedded Quantum-Error Correction. J Phys Chem Lett 2020; 11:8610-8615. [PMID: 32936660 PMCID: PMC8011924 DOI: 10.1021/acs.jpclett.0c02213] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 09/16/2020] [Indexed: 05/17/2023]
Abstract
We show that molecular nanomagnets have a potential advantage in the crucial rush toward quantum computers. Indeed, the sizable number of accessible low-energy states of these systems can be exploited to define qubits with embedded quantum error correction. We derive the scheme to achieve this crucial objective and the corresponding sequence of microwave/radiofrequency pulses needed for the error correction procedure. The effectiveness of our approach is shown already with a minimal S = 3/2 unit corresponding to an existing molecule, and the scaling to larger spin systems is quantitatively analyzed.
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Affiliation(s)
- A. Chiesa
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - E. Macaluso
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - F. Petiziol
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - S. Wimberger
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- INFN,
Sezione di Milano Bicocca, Gruppo Collegato
di Parma, Parma, Italy
| | - P. Santini
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - S. Carretta
- Dipartimento
di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
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8
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Garlatti E, Allodi G, Bordignon S, Bordonali L, Timco GA, Winpenny REP, Lascialfari A, De Renzi R, Carretta S. Breaking the ring: 53Cr-NMR on the Cr 8Cd molecular nanomagnet. J Phys Condens Matter 2020; 32:244003. [PMID: 32079012 DOI: 10.1088/1361-648x/ab7872] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
An accurate experimental characterization of finite antiferromagnetic (AF) spin chains is crucial for controlling and manipulating their magnetic properties and quantum states for potential applications in spintronics or quantum computation. In particular, finite AF chains are expected to show a different magnetic behaviour depending on their length and topology. Molecular AF rings are able to combine the quantum-magnetic behaviour of AF chains with a very remarkable tunability of their topological and geometrical properties. In this work we measure the 53Cr-NMR spectra of the Cr8Cd ring to study the local spin densities on the Cr sites. Cr8Cd can in fact be considered a model system of a finite AF open chain with an even number of spins. The NMR resonant frequencies are in good agreement with the theoretical local spin densities, by assuming a core polarization field A C = -12.7 T μ B -1. Moreover, these NMR results confirm the theoretically predicted non-collinear spin arrangement along the Cr8Cd ring, which is typical of an even-open AF spin chain.
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Affiliation(s)
- E Garlatti
- Dipartimento di Science Matematiche, Fisiche e Informatiche, Università di Parma, Parco Area delle Scienze 7/A, 43124 Parma, Italy
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9
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Garlatti E, Tesi L, Lunghi A, Atzori M, Voneshen DJ, Santini P, Sanvito S, Guidi T, Sessoli R, Carretta S. Unveiling phonons in a molecular qubit with four-dimensional inelastic neutron scattering and density functional theory. Nat Commun 2020; 11:1751. [PMID: 32273510 PMCID: PMC7145838 DOI: 10.1038/s41467-020-15475-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 03/05/2020] [Indexed: 11/09/2022] Open
Abstract
Phonons are the main source of relaxation in molecular nanomagnets, and different mechanisms have been proposed in order to explain the wealth of experimental findings. However, very limited experimental investigations on phonons in these systems have been performed so far, yielding no information about their dispersions. Here we exploit state-of-the-art single-crystal inelastic neutron scattering to directly measure for the first time phonon dispersions in a prototypical molecular qubit. Both acoustic and optical branches are detected in crystals of [VO(acac)[Formula: see text]] along different directions in the reciprocal space. Using energies and polarisation vectors calculated with state-of-the-art Density Functional Theory, we reproduce important qualitative features of [VO(acac)[Formula: see text]] phonon modes, such as the presence of low-lying optical branches. Moreover, we evidence phonon anti-crossings involving acoustic and optical branches, yielding significant transfers of the spin-phonon coupling strength between the different modes.
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Affiliation(s)
- E Garlatti
- ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK.,Dipartimento di Science Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, Parco Area delle Scienze 7/A, 43124, Parma, Italy
| | - L Tesi
- Dipartimento di Chimica U. Schiff, Università degli Studi di Firenze and UdR Firenze, INSTM, Via della Lastruccia 3, I50019, Sesto Fiorentino, Firenze, Italy.,Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - A Lunghi
- School of Physics, CRANN and AMBER Trinity College, Dublin 2, Ireland
| | - M Atzori
- Dipartimento di Chimica U. Schiff, Università degli Studi di Firenze and UdR Firenze, INSTM, Via della Lastruccia 3, I50019, Sesto Fiorentino, Firenze, Italy.,Laboratoire National des Champs Magnétiques Intenses (LNCMI) - CNRS, 25 rue des Martyrs, 38042, Grenoble, France
| | - D J Voneshen
- ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK
| | - P Santini
- Dipartimento di Science Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, Parco Area delle Scienze 7/A, 43124, Parma, Italy
| | - S Sanvito
- School of Physics, CRANN and AMBER Trinity College, Dublin 2, Ireland
| | - T Guidi
- ISIS Facility, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK.
| | - R Sessoli
- Dipartimento di Chimica U. Schiff, Università degli Studi di Firenze and UdR Firenze, INSTM, Via della Lastruccia 3, I50019, Sesto Fiorentino, Firenze, Italy.
| | - S Carretta
- Dipartimento di Science Matematiche, Fisiche e Informatiche, Università di Parma and UdR Parma, INSTM, Parco Area delle Scienze 7/A, 43124, Parma, Italy.
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10
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Chiesa A, Guidi T, Carretta S, Ansbro S, Timco GA, Vitorica-Yrezabal I, Garlatti E, Amoretti G, Winpenny REP, Santini P. Magnetic Exchange Interactions in the Molecular Nanomagnet Mn_{12}. Phys Rev Lett 2017; 119:217202. [PMID: 29219408 DOI: 10.1103/physrevlett.119.217202] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Indexed: 06/07/2023]
Abstract
The discovery of magnetic bistability in Mn_{12} more than 20 years ago marked the birth of molecular magnetism, an extremely fertile interdisciplinary field and a powerful route to create tailored magnetic nanostructures. However, the difficulty to determine interactions in complex polycentric molecules often prevents their understanding. Mn_{12} is an outstanding example of this difficulty: although it is the forefather and most studied of all molecular nanomagnets, an unambiguous determination of even the leading magnetic exchange interactions is still lacking. Here we exploit four-dimensional inelastic neutron scattering to portray how individual spins fluctuate around the magnetic ground state, thus fixing the exchange couplings of Mn_{12} for the first time. Our results demonstrate the power of four-dimensional inelastic neutron scattering as an unrivaled tool to characterize magnetic clusters.
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Affiliation(s)
- A Chiesa
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
- Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - T Guidi
- ISIS Facility, Rutherford Appleton Laboratory, OX11 0QX Didcot, United Kingdom
| | - S Carretta
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
| | - S Ansbro
- School of Chemistry and Photon Science Institute, University of Manchester, M13 9PL Manchester, United Kingdom
- Institut Laue-Langevin, 71 Avenue des Martyrs CS 20156, Grenoble Cedex 9 F-38042, France
| | - G A Timco
- School of Chemistry and Photon Science Institute, University of Manchester, M13 9PL Manchester, United Kingdom
| | - I Vitorica-Yrezabal
- School of Chemistry and Photon Science Institute, University of Manchester, M13 9PL Manchester, United Kingdom
| | - E Garlatti
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
| | - G Amoretti
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
| | - R E P Winpenny
- School of Chemistry and Photon Science Institute, University of Manchester, M13 9PL Manchester, United Kingdom
| | - P Santini
- Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy
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11
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Bordonali L, Garlatti E, Casadei CM, Furukawa Y, Lascialfari A, Carretta S, Troiani F, Timco G, Winpenny REP, Borsa F. Magnetic properties and hyperfine interactions in Cr8, Cr7Cd, and Cr7Ni molecular rings from 19F-NMR. J Chem Phys 2014; 140:144306. [DOI: 10.1063/1.4870469] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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Carretta S, Amoretti G, Santini P, Mougel V, Mazzanti M, Gambarelli S, Colineau E, Caciuffo R. Magnetic properties and chiral states of a trimetallic uranium complex. J Phys Condens Matter 2013; 25:486001. [PMID: 24169692 DOI: 10.1088/0953-8984/25/48/486001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The magnetic properties of the triangular molecular nanomagnet [UO2L]3 (L = 2-(4-tolyl)-1,3-bis(quinolyl)malondiiminate) have been investigated through electron paramagnetic resonance spectroscopy, high-field magnetization and susceptibility measurements. The experimental findings are well reproduced by a microscopic model including exchange interactions and local crystal fields. These results show that [UO2L]3 is characterized by a non-magnetic ground doublet corresponding to two oppositely twisted chiral arrangements of the uranium moments. The non-axial character of single-ion crystal fields leads to quantum tunneling of the noncollinear magnetization in the presence of a magnetic field applied perpendicularly to the triangle plane.
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Affiliation(s)
- S Carretta
- Dipartimento di Fisica e Scienze della Terra, Università di Parma, and Unità CNISM di Parma, Viale G P Usberti 7/A, I-43124 Parma, Italy
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13
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Carretta S, Chiesa A, Troiani F, Gerace D, Amoretti G, Santini P. Quantum information processing with hybrid spin-photon qubit encoding. Phys Rev Lett 2013; 111:110501. [PMID: 24074061 DOI: 10.1103/physrevlett.111.110501] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Indexed: 06/02/2023]
Abstract
We introduce a scheme to perform quantum information processing that is based on a hybrid spin-photon qubit encoding. The proposed qubits consist of spin ensembles coherently coupled to microwave photons in coplanar waveguide resonators. The quantum gates are performed solely by shifting the resonance frequencies of the resonators on a nanosecond time scale. An additional cavity containing a Cooper-pair box is exploited as an auxiliary degree of freedom to implement two-qubit gates. The generality of the scheme allows its potential implementation with a wide class of spin systems.
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Affiliation(s)
- S Carretta
- Dipartimento di Fisica e Scienze della Terra, Università di Parma, I-43124 Parma, Italy
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14
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Abstract
We present a flexible and effective ab initio scheme to build many-body models for molecular nanomagnets, and to calculate magnetic exchange couplings and zero-field splittings. It is based on using localized Foster-Boys orbitals as a one-electron basis. We apply this scheme to three paradigmatic systems, the antiferromagnetic rings Cr8 and Cr7Ni, and the single-molecule magnet Fe4. In all cases we identify the essential magnetic interactions and find excellent agreement with experiments.
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Affiliation(s)
- A Chiesa
- Dipartimento di Fisica e Scienze della Terra, University of Parma, 43124 Parma, Italy and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - S Carretta
- Dipartimento di Fisica e Scienze della Terra, University of Parma, 43124 Parma, Italy
| | - P Santini
- Dipartimento di Fisica e Scienze della Terra, University of Parma, 43124 Parma, Italy
| | - G Amoretti
- Dipartimento di Fisica e Scienze della Terra, University of Parma, 43124 Parma, Italy
| | - E Pavarini
- Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany and JARA High-Performance Computing, RWTH Aachen University, 52062 Aachen, Germany
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15
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Casadei CM, Bordonali L, Furukawa Y, Borsa F, Garlatti E, Lascialfari A, Carretta S, Sanna S, Timco G, Winpenny R. Local spin density in the Cr7Ni antiferromagnetic molecular ring and 53Cr-NMR. J Phys Condens Matter 2012; 24:406002. [PMID: 22971620 DOI: 10.1088/0953-8984/24/40/406002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present (53)Cr-NMR spectra collected at low temperature in a single crystal of the heterometallic antiferromagnetic (AF) ring Cr(7)Ni in the S = 1/2 ground state with the aim of establishing the distribution of the local electronic moment in the ring. Due to the poor S/N we observed only one signal which is ascribed to three almost equivalent (53)Cr nuclei in the ring. The calculated spin density in Cr(7)Ni in the ground state, with the applied magnetic field both parallel and perpendicular to the plane of the ring, turns out to be AF staggered with the greatest component of the local spin <s> for the Cr(3+) ions next to the Ni(2+) ion. The (53)Cr-NMR frequency was found to be in good agreement with the local spin density calculated theoretically by assuming a core polarization field of H(cp) = - 11 T/μ(B) for both orientations, close to the value found previously in Cr(7)Cd. The observed orientation dependence of the local spin moments is well reproduced by the theoretical calculation and evidences the importance of single-ion and dipolar anisotropies.
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Affiliation(s)
- C M Casadei
- CNISM and Department of Physics, Università degli Studi di Pavia, I-27100 Pavia, Italy
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16
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Garlatti E, Carretta S, Affronte M, Sañudo EC, Amoretti G, Santini P. Magnetic properties and relaxation dynamics of a frustrated Ni₇ molecular nanomagnet. J Phys Condens Matter 2012; 24:104006. [PMID: 22354893 DOI: 10.1088/0953-8984/24/10/104006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The Ni₇ nanomagnet represents an ideal model system for investigating the effects of geometrical frustration in magnetic interactions. The Ni ions in the magnetic core are arranged on two corner-sharing tetrahedra and interact through antiferromagnetic exchange couplings. We show that the high degree of frustration leads to a magnetic energy spectrum with large degeneracies which result in unusual static and dynamical magnetic properties. In particular, the relaxation dynamics of the magnetization is characterized by several distinct characteristic times. We also discuss the possible interest of Ni₇ for magnetocaloric refrigeration.
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Affiliation(s)
- E Garlatti
- Dipartimento di Scienze Molecolari Applicate ai Biosistemi, Universit`a di Milano, via Trentacoste 2, I-20134 Milano, Italy
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17
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Abstract
Quantum simulators are controllable systems that can be used to simulate other quantum systems. Here we focus on the dynamics of a chain of molecular qubits with interposed antiferromagnetic dimers. We theoretically show that its dynamics can be controlled by means of uniform magnetic pulses and used to mimic the evolution of other quantum systems, including fermionic ones. We propose two proof-of-principle experiments based on the simulation of the Ising model in a transverse field and of the quantum tunneling of the magnetization in a spin-1 system.
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Affiliation(s)
- P Santini
- Dipartimento di Fisica, Università di Parma, Viale G. P. Usberti 7/A, I-43124 Parma, Italy
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18
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Gillon B, Guidi T, Carretta S, Timco G, Mason S, Stunault A, Bianchi A, Santini P, Cousson A, Winpenny R. Finite size effects in a quantum chain of antiferromagnetically coupled spins 3/2. Acta Crystallogr A 2011. [DOI: 10.1107/s0108767311096292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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19
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Mason K, Chang J, Garlatti E, Prescimone A, Yoshii S, Nojiri H, Schnack J, Tasker PA, Carretta S, Brechin EK. Linking [FeIII3] triangles with “double-headed”phenolic oximes. Chem Commun (Camb) 2011; 47:6018-20. [DOI: 10.1039/c1cc11146a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Abstract
In presence of active orbital degrees of freedom, elementary excitations around a broken-symmetry state may include multipolar waves, but none of these exotic dispersive excitation branches has ever been identified. We show that quadrupolar waves constitute a major component of the dynamics of uranium dioxide in its magnetoquadrupolar ordered phase, and that many unexplained features in existing inelastic neutron scattering data, including a whole excitation branch, are associated with these propagating quadrupolar fluctuations. Our model permits us to separate the role of Jahn-Teller and superexchange mechanisms as sources of quadrupolar interactions.
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Affiliation(s)
- S Carretta
- Dipartimento di Fisica, Università di Parma, and Unità CNISM di Parma, Viale G. P. Usberti 7/A, I-43100 Parma, Italy
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21
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Candini A, Lorusso G, Troiani F, Ghirri A, Carretta S, Santini P, Amoretti G, Muryn C, Tuna F, Timco G, McInnes EJL, Winpenny REP, Wernsdorfer W, Affronte M. Entanglement in supramolecular spin systems of two weakly coupled antiferromagnetic rings (purple-Cr7Ni). Phys Rev Lett 2010; 104:037203. [PMID: 20366678 DOI: 10.1103/physrevlett.104.037203] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 08/28/2009] [Indexed: 05/29/2023]
Abstract
We characterize supramolecular magnetic structures, consisting of two weakly coupled antiferromagnetic rings, by low-temperature specific heat, susceptibility, magnetization and electron paramagnetic resonance measurements. Intra- and inter-ring interactions are modeled through a microscopic spin-Hamiltonian approach that reproduces all the experimental data quantitatively and legitimates the use of an effective two-qubit picture. Spin entanglement between the rings is experimentally demonstrated through magnetic susceptibility below 50 mK and theoretically quantified by the concurrence.
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Affiliation(s)
- A Candini
- National Research Center on nanoStructures and bioSystems at Surfaces (S3), CNR-INFM, 41100 Modena, Italy
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22
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Carretta S, Bianchi A, Santini P, Amoretti G. Relaxation dynamics of the Fe8 molecular nanomagnet as probed by nuclear magnetic resonance. Dalton Trans 2010; 39:4869-73. [DOI: 10.1039/b927000k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Belesi M, Micotti E, Mariani M, Borsa F, Lascialfari A, Carretta S, Santini P, Amoretti G, McInnes EJL, Tidmarsh IS, Hawkett JR. Unconventional nonequilibrium dynamics in Ni10 magnetic molecules: evidence from NMR. Phys Rev Lett 2009; 102:177201. [PMID: 19518820 DOI: 10.1103/physrevlett.102.177201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Indexed: 05/27/2023]
Abstract
Crystals containing Ni10 magnetic molecules display an unprecedented form of out-of-equilibrium behavior of the bulk magnetization M at temperatures as high as 17 K. We have performed 1H NMR measurements to probe the local Ni magnetic moments and their dynamics. It is apparent that no freezing of the Ni moments occurs, in striking contrast to what is observed in blocked superparamagnetic systems. The average local moments display the same behavior as M, thus unambiguously demonstrating the intrinsic character of the phenomenon. This result supports the hypothesis that the slowing down of M is due to a resonant phonon trapping mechanism which prevents the thermalization of M but not the fast spin flippings of the individual molecular moments. Indeed, the measured nuclear spin-lattice relaxation rate points to fast single-molecule dynamics at low temperature.
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Affiliation(s)
- M Belesi
- Dipartimento di Fisica A.Volta, Università di Pavia, I-27100 Pavia and S3-CNR-INFM, Modena, Italy
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24
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Amoretti G, Caciuffo R, Carretta S, Guidi T, Magnani N, Santini P. Inelastic neutron scattering investigations of molecular nanomagnets. Inorganica Chim Acta 2008. [DOI: 10.1016/j.ica.2008.03.047] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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25
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Carretta S, Guidi T, Santini P, Amoretti G, Pieper O, Lake B, van Slageren J, El Hallak F, Wernsdorfer W, Mutka H, Russina M, Milios CJ, Brechin EK. Breakdown of the giant spin model in the magnetic relaxation of the Mn6 nanomagnets. Phys Rev Lett 2008; 100:157203. [PMID: 18518147 DOI: 10.1103/physrevlett.100.157203] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Indexed: 05/26/2023]
Abstract
We study the spin dynamics in two variants of the high-anisotropy Mn6 nanomagnet by inelastic neutron scattering, magnetic resonance spectroscopy and magnetometry. We show that a giant-spin picture is completely inadequate for these systems and that excited S multiplets play a key role in determining the effective energy barrier for the magnetization reversal. Moreover, we demonstrate the occurrence of tunneling processes involving pair of states having different total spin.
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Affiliation(s)
- S Carretta
- Dipartimento di Fisica, Università di Parma, Parma, Italy
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26
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Carretta S, Santini P, Amoretti G, Guidi T, Copley JRD, Qiu Y, Caciuffo R, Timco G, Winpenny REP. Quantum oscillations of the total spin in a heterometallic antiferromagnetic ring: evidence from neutron spectroscopy. Phys Rev Lett 2007; 98:167401. [PMID: 17501458 DOI: 10.1103/physrevlett.98.167401] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Indexed: 05/15/2023]
Abstract
Using inelastic neutron scattering and applied fields up to 11.4 T, we have studied the spin dynamics of the Cr7Ni antiferromagnetic ring in the energy window 0.05-1.6 meV. We demonstrate that the external magnetic field induces an avoided crossing (anticrossing) between energy levels with different total-spin quantum numbers. This corresponds to quantum oscillations of the total spin of each molecule. The inelastic character of the observed excitation and the field dependence of its linewidth indicate that molecular spins oscillate coherently for a significant number of cycles. Precise signatures of the anticrossing are also found at higher energy, where measured and calculated spectra match very well.
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Affiliation(s)
- S Carretta
- Dipartimento di Fisica, Università di Parma, I-43100 Parma, Italy
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27
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Micotti E, Furukawa Y, Kumagai K, Carretta S, Lascialfari A, Borsa F, Timco GA, Winpenny REP. Local spin moment distribution in antiferromagnetic molecular rings probed by NMR. Phys Rev Lett 2006; 97:267204. [PMID: 17280461 DOI: 10.1103/physrevlett.97.267204] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Indexed: 05/13/2023]
Abstract
The NMR spectra of 19F and 53Cr have been obtained at low temperatures in a heterometallic substituted antiferromagnetic (AF) ring Cr7Cd with an S=3/2 ground state and compared with the spectra in a homometallic Cr8 AF ring with an S=0 ground state. From the analysis of the spectra one can derive directly model independent values of the staggered nonuniform distribution of the local moment in the heterometallic ring Cr7Cd. The experimental values are found to be in excellent agreement with the theoretical values calculated on the basis of an effective spin Hamiltonian which includes crystal field effects.
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Affiliation(s)
- E Micotti
- Department of Physics "A. Volta" and CNR-INFM, Via Bassi 6, I-27100 Pavia, Italy and Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
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28
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Santini P, Carretta S, Magnani N, Amoretti G, Caciuffo R. Hidden order and low-energy excitations in NpO2. Phys Rev Lett 2006; 97:207203. [PMID: 17155710 DOI: 10.1103/physrevlett.97.207203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Indexed: 05/12/2023]
Abstract
We investigate the nature of the hidden order parameter in the ordered phase of NpO2, which had been identified with a staggered arrangement of Gamma5 magnetic multipoles. By analyzing the existing experimental data, we show that the most likely driving order parameter is not provided by octupoles, as usually assumed, but rather by the rank-5 triakontadipoles. Calculations of the coupled dynamics of spins, Gamma5 quadrupoles, and Gamma5 triakontadipoles in the ordered phase enable us to analyze the resulting structure of low-energy excitations. We show that the powder inelastic neutron scattering cross section should contain, in addition to the already-observed peak at 6.5 meV, a second weaker peak at about 14 meV.
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Affiliation(s)
- P Santini
- Dipartimento di Fisica, Università di Parma, I-43100 Parma, Italy
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29
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Carretta S, Santini P, Amoretti G, Affronte M, Candini A, Ghirri A, Tidmarsh IS, Laye RH, Shaw R, McInnes EJL. High-temperature slow relaxation of the magnetization in Ni10 magnetic molecules. Phys Rev Lett 2006; 97:207201. [PMID: 17155708 DOI: 10.1103/physrevlett.97.207201] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Indexed: 05/12/2023]
Abstract
We investigate a family of molecular crystals containing noninteracting Ni10 magnetic molecules. We find slow relaxation of the magnetization below a temperature as high as 17 K and we show that this behavior is not associated with an anisotropy energy barrier. Ni10 has a characteristic magnetic energy spectrum structured in dense bands, the lowest of which makes the crystal opaque to phonons of energy below about 1 meV. We ascribe the nonequilibrium behavior to the resulting resonant trapping of these low-energy phonons. Trapping breaks up spin relaxation paths leading to a novel kind of slow magnetic dynamics which occurs in the lack of anisotropy, magnetic interactions and quenched disorder.
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Affiliation(s)
- S Carretta
- Dipartimento di Fisica, Università di Parma, I-43100 Parma, Italy
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30
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Troiani F, Ghirri A, Affronte M, Carretta S, Santini P, Amoretti G, Piligkos S, Timco G, Winpenny REP. Molecular engineering of antiferromagnetic rings for quantum computation. Phys Rev Lett 2005; 94:207208. [PMID: 16090284 DOI: 10.1103/physrevlett.94.207208] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2004] [Indexed: 05/03/2023]
Abstract
The substitution of one metal ion in a Cr-based molecular ring with dominant antiferromagnetic couplings allows the engineering of its level structure and ground-state degeneracy. Here we characterize a Cr7Ni molecular ring by means of low-temperature specific-heat and torque-magnetometry measurements, thus determining the microscopic parameters of the corresponding spin Hamiltonian. The energy spectrum and the suppression of the leakage-inducing S mixing render the Cr7Ni molecule a suitable candidate for the qubit implementation, as further substantiated by our quantum-gate simulations.
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Affiliation(s)
- F Troiani
- INFM-S3 National Research Center on nanoStructures and bioSystems at Surfaces and Dipartimento di Fisica, Università di Modena e Reggio Emilia, via G. Campi 213/A, I-41100 Modena, Italy.
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31
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Santini P, Carretta S, Liviotti E, Amoretti G, Carretta P, Filibian M, Lascialfari A, Micotti E. NMR as a probe of the relaxation of the magnetization in magnetic molecules. Phys Rev Lett 2005; 94:077203. [PMID: 15783849 DOI: 10.1103/physrevlett.94.077203] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Indexed: 05/24/2023]
Abstract
We investigate the time autocorrelation of the molecular magnetization M(t) for three classes of magnetic molecules (antiferromagnetic rings, grids, and nanomagnets), in contact with the phonon heat bath. For all three classes, we find that the exponential decay of the fluctuations of M(t) is characterized by a single characteristic time tau(T,B) for not too high temperature T and field B. This is reflected in a nearly single-Lorentzian shape of the spectral density of the fluctuations. We show that such fluctuations are effectively probed by NMR, and that our theory explains the recent phenomenological observation by Baek et al. [Phys. Rev. B 70, 134434 (2004)] that the Larmor-frequency dependence of 1/T(1) data in a large number of AFM rings fits to a single-Lorentzian form.
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Affiliation(s)
- P Santini
- INFM and Dipartimento di Fisica, Università di Parma, I-43100 Parma, Italy
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32
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Carretta S, Liviotti E, Magnani N, Santini P, Amoretti G. S mixing and quantum tunneling of the magnetization in molecular nanomagnets. Phys Rev Lett 2004; 92:207205. [PMID: 15169380 DOI: 10.1103/physrevlett.92.207205] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Indexed: 05/24/2023]
Abstract
The role of S mixing in the quantum tunneling of the magnetization in nanomagnets has been investigated. We show that the effect on the tunneling frequency is huge and that the discrepancy (more than 3 orders of magnitude in the tunneling frequency) between spectroscopic and relaxation measurements in Fe(8) can be resolved if S mixing is taken into account.
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Affiliation(s)
- S Carretta
- Istituto Nazionale per la Fisica della Materia, Dipartimento di Fisica, Università di Parma, I-43100 Parma, Italy
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33
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Waldmann O, Carretta S, Santini P, Koch R, Jansen AGM, Amoretti G, Caciuffo R, Zhao L, Thompson LK. Quantum magneto-oscillations in a supramolecular Mn(II)-[3 x 3] grid. Phys Rev Lett 2004; 92:096403. [PMID: 15089497 DOI: 10.1103/physrevlett.92.096403] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Indexed: 05/24/2023]
Abstract
The magnetic grid molecule Mn(II)-[3 x 3] has been studied by high-field torque magnetometry at 3He temperatures. At fields above 5 T, the torque versus field curves exhibit an unprecedented oscillatory behavior. A model is proposed which describes these magneto-oscillations well.
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Affiliation(s)
- O Waldmann
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
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34
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Waldmann O, Guidi T, Carretta S, Mondelli C, Dearden AL. Elementary excitations in the cyclic molecular nanomagnet Cr8. Phys Rev Lett 2003; 91:237202. [PMID: 14683210 DOI: 10.1103/physrevlett.91.237202] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2003] [Indexed: 05/24/2023]
Abstract
Combining recent and new inelastic neutron scattering data for the molecular cyclic cluster Cr8 produces a deep understanding of the low lying excitations in bipartite antiferromagnetic Heisenberg rings. The existence of the L band, the lowest rotational band, and the E band, essentially spin wave excitations, is confirmed spectroscopically. The different significance of these excitations and their physical nature is clearly established by high-energy and Q-dependence data.
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Affiliation(s)
- O Waldmann
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
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35
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Liviotti E, Carretta S, Amoretti G. S-mixing contributions to the high-order anisotropy terms in the effective spin Hamiltonian for magnetic clusters. J Chem Phys 2002. [DOI: 10.1063/1.1492796] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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