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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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Garlatti E, Chiesa A, Bonfà P, Macaluso E, Onuorah IJ, Parmar VS, Ding YS, Zheng YZ, Giansiracusa MJ, Reta D, Pavarini E, Guidi T, Mills DP, Chilton NF, Winpenny REP, Santini P, Carretta S. A Cost-Effective Semi-Ab Initio Approach to Model Relaxation in Rare-Earth Single-Molecule Magnets. J Phys Chem Lett 2021; 12:8826-8832. [PMID: 34491740 PMCID: PMC8450932 DOI: 10.1021/acs.jpclett.1c02367] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 09/01/2021] [Indexed: 05/30/2023]
Abstract
We discuss a cost-effective approach to understand magnetic relaxation in the new generation of rare-earth single-molecule magnets. It combines ab initio calculations of the crystal field parameters, of the magneto-elastic coupling with local modes, and of the phonon density of states with fitting of only three microscopic parameters. Although much less demanding than a fully ab initio approach, the method gives important physical insights into the origin of the observed relaxation. By applying it to high-anisotropy compounds with very different relaxation, we demonstrate the power of the approach and pinpoint ingredients for improving the performance of single-molecule magnets.
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Affiliation(s)
- Elena Garlatti
- Universitá
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - Alessandro Chiesa
- Universitá
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - Pietro Bonfà
- Universitá
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, 43124 Parma, Italy
| | - Emilio Macaluso
- Universitá
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - Ifeanyi J. Onuorah
- Universitá
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, 43124 Parma, Italy
| | - Vijay S. Parmar
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - You-Song Ding
- Frontier
Institute of Science and Technology, Xi’an
Jiaotong University, 99 Yanxiang Road, 710054 Xi’an, Shaanxi, China
| | - Yan-Zhen Zheng
- Frontier
Institute of Science and Technology, Xi’an
Jiaotong University, 99 Yanxiang Road, 710054 Xi’an, Shaanxi, China
| | - Marcus J. Giansiracusa
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Daniel Reta
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Eva Pavarini
- Institute
for Advanced Simulations, Forschungszentrum
Juelich, 52428 Juelich, Germany
- JARA
High-Performance Computing, RWTH Aachen
University, 52062 Aachen, Germany
| | - Tatiana Guidi
- ISIS
Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, U.K.
| | - David P. Mills
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Nicholas F. Chilton
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Richard E. P. Winpenny
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Paolo Santini
- Universitá
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
| | - Stefano Carretta
- Universitá
di Parma, Dipartimento di
Scienze Matematiche, Fisiche e Informatiche, 43124 Parma, Italy
- UdR
Parma, INSTM, I-43124 Parma, Italy
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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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Adelnia F, Bordonali L, Mariani M, Bordignon S, Timco G, Winpenny R, Borsa F, Lascialfari A. Comparison of spin dynamics and magnetic properties in antiferromagnetic closed and open molecular Cr-based rings. J Phys Condens Matter 2015; 27:506001. [PMID: 26609709 DOI: 10.1088/0953-8984/27/50/506001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present magnetization and (1)H nuclear magnetic resonance (NMR) measurements performed in both closed Cr8 and open Cr8Zn antiferromagnetic molecular rings in the temperature range 1.65 < T < 300 K at different external magnetic fields. The magnetization measurements on Cr8Zn are consistent with a small decrease of the exchange constant J(Cr-Cr) and a much smaller gap between the singlet ground state and the first magnetic excited state when compared with the same properties of the closed ring Cr8, in agreement with previous inelastic neutron scattering results. The temperature dependence of the (1)H NMR nuclear spin lattice relaxation rate (NSLR), 1/T1(T), was found to be similar in both open and closed rings with a magnetic field dependent peak centered at a temperature of the order of the corresponding exchange constant J(Cr-Cr). Such main peak in the NSLR could be fitted with a single correlation frequency ω(c1) as in most molecular magnets. At low temperature T < 4 K, a new feature not observed in previous NMR measurements on antiferromagnetic rings and consisting in a smaller peak of 1/T1(T) which is well resolved only in Cr8Zn, was singled out. This low-T peak indicates the presence of a second correlation frequency ω(c2) of the magnetization, found to be quite different between the two rings and thus possibly reflecting the different low temperature level structure associated with the different spin topology. The presence of ω(c2) is confirmed by the NMR spin-spin relaxation rate enhancement, which generates a two-steps wipe-out effect of the NMR signal intensity.
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Affiliation(s)
- Fatemeh Adelnia
- Dipartimento di Fisica, Università degli Studi di Milano and INSTM, I-20133 Milano, Italy. Dipartimento di Fisica, Università degli Studi di Pavia and INSTM, I-27100 Pavia, Italy
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Ghirri A, Chiesa A, Carretta S, Troiani F, van Tol J, Hill S, Vitorica-Yrezabal I, Timco GA, Winpenny REP, Affronte M. Coherent Spin Dynamics in Molecular Cr8Zn Wheels. J Phys Chem Lett 2015; 6:5062-6. [PMID: 26633293 DOI: 10.1021/acs.jpclett.5b02527] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Controlling and understanding transitions between molecular spin states allows selection of the most suitable ones for qubit encoding. Here we present a detailed investigation of single crystals of a polynuclear Cr8Zn molecular wheel using 241 GHz electron paramagnetic resonance (EPR) spectroscopy in high magnetic field. Continuous wave spectra are well reproduced by spin Hamiltonian calculations, which evidence that transitions in correspondence to a well-defined anticrossing involve mixed states with different total spin. We studied, by means of spin echo experiments, the temperature dependence of the dephasing time (T2) down to 1.35 K. These results are reproduced by considering both hyperfine and intermolecular dipolar interactions, evidencing that the dipolar contribution is completely suppressed at the lowest temperature. Overall, these results shed light on the effects of the decoherence mechanisms, whose understanding is crucial to exploit chemically engineered molecular states as a resource for quantum information processing.
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Affiliation(s)
- Alberto Ghirri
- Istituto Nanoscienze-CNR , via G. Campi 213A, 41125 Modena, Italy
| | - Alessandro Chiesa
- Dipartimento di Fisica e Scienze della Terra, Università di Parma , Parco Area delle Scienze 7/a, 43123 Parma, Italy
| | - Stefano Carretta
- Dipartimento di Fisica e Scienze della Terra, Università di Parma , Parco Area delle Scienze 7/a, 43123 Parma, Italy
| | - Filippo Troiani
- Istituto Nanoscienze-CNR , via G. Campi 213A, 41125 Modena, Italy
| | - Johan van Tol
- National High Magnetic Field Laboratory , Tallahassee, Florida 32310, United States
| | - Stephen Hill
- National High Magnetic Field Laboratory , Tallahassee, Florida 32310, United States
- Department of Physics, Florida State University , Tallahassee, Florida 32306, United States
| | - Inigo Vitorica-Yrezabal
- School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Grigore A Timco
- School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Richard E P Winpenny
- School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom
| | - Marco Affronte
- Istituto Nanoscienze-CNR , via G. Campi 213A, 41125 Modena, Italy
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia , via Campi 213A, 41125 Modena, Italy
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Furukawa Y, Fang X, Kögerler P. Spin dynamics of the giant polyoxometalate molecule {Mn₄₀W₂₂₄} studied by NMR. J Phys Condens Matter 2014; 26:196003. [PMID: 24762855 DOI: 10.1088/0953-8984/26/19/196003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
(7)Li nuclear magnetic resonance (NMR) studies have been performed to investigate magnetic properties and spin dynamics of Mn(3+) (S = 2) spins in the giant polyoxometalate molecule {Mn₄₀W₂₂₄}. The (7)Li-NMR line width is proportional to the external magnetic field H as expected in a paramagnetic state above 3 K. Below this temperature the line width shows a sudden increase and is almost independent of H, which indicates freezing of the local Mn(3+) spins. The temperature dependence of T₁ for both (1)H and (7)Li reveals slow spin dynamics at low temperatures, consistent with spin freezing. The slow spin dynamics is also evidenced by the observation of a peak of 1/T₂ around 3 K, where the fluctuation frequency of spins is of the order of ∼200 kHz. An explicit form of the temperature dependence of the fluctuation frequency of Mn(3+) spins is derived from the nuclear relaxation data.
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Affiliation(s)
- Y Furukawa
- Ames Laboratory, US DOE, Iowa State University, Ames, Iowa 50011, USA. Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
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Abstract
We present a theory of nuclear magnetic resonance shielding tensors for electronic states with arbitrary degeneracy. The shieldings are here expressed in terms of generalized Zeeman (g((k))) and hyperfine (A((k))) tensors, of all ranks k allowed by the size of degeneracy. Contrary to recent proposals [T. O. Pennanen and J. Vaara, Phys. Rev. Lett. 100, 133002 (2008)], our theory is valid in the strong spin-orbit coupling limit. Ab initio calculations for the fourfold degenerate Γ(8) ground state of lanthanide-doped fluorite crystals CaF(2):Ln (Ln=Pr(2+), Nd(3+), Sm(3+), and Dy(3+)) show that previously neglected contributions can account for more than 50% of the paramagnetic shift.
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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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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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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 C, Brechin E. Neutron spectroscopy and magnetic relaxation of the Mn6 nanomagnets. Polyhedron 2009; 28:1940-4. [DOI: 10.1016/j.poly.2008.11.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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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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Prando G, Carretta P, Giblin SR, Lago J, Pin S, Ghigna P. Dilution effects in Ho2-xYxSn2O7: From the spin ice to the single-ion magnet. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/145/1/012033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Mariani M, Aldrovandi S, Corti M, Lascialfari A, Bogani L, Caneschi A, Sessoli R. Local spin dynamics in doped cobalt(II)-radical magnetic chains studied by 1H NMR. Inorganica Chim Acta 2008. [DOI: 10.1016/j.ica.2008.03.102] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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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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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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