Comptes Rendus
no. 9
Quantum nanomagnet
[Nano-aimants quantiques]
Bernard Barbara1
1 Laboratoire Louis-Néel, CNRS, BP166, 38042 Grenoble cedex 09, France
Comptes Rendus. Physique, Volume 6 (2005) no. 9, pp. 934-944.

Un monocristal de nanoaimants est un objet quantique macroscopique. Le premier objet de cette classe qui ait été découvert est le complexe moléculaire Mn12-ac, de spin S=10 par molécule. Avec des écarts tunnels extrêmement petits, ce système a ouvert le domaine de la dynamique quantique lente (incohérente) permettant, entre autre, l'étude d'effets réciproques entre magnétisme classique et quantique. La première partie de cet article donne une vue d'ensemble de ce nouveau type de mésoscopie. Une extension au cas des ions de Terres Rares est présentée dans la seconde partie. Elle montre que le magnétisme mésoscopique peut atteindre l'échelle atomique. Des modifications se produisent dans le bain de spin, qui permettent l'observation d'états intriqués à deux ou quatre corps. Ce domaine est étroitement connecté à celui des mémoires quantiques pour le calcul quantique à l'état solide.

A single crystal made of nanomagnets is a macroscopic quantum object. The first of this class to have been discovered is the so-called molecular complex Mn12-ac with a spin S=10 per molecule. With vanishingly small tunneling gaps this system opened the field of slow quantum dynamics (incoherent), with the study of interplays between classical and quantum magnetism in particular. The first part of this article gives an overview of this new type of mesoscopy. An extension to the case of non-interacting rare-earth ions is presented in the second part, showing that mesoscopic magnetism can reach the atomic scale. Modifications occur in the spin-bath, allowing the observation of two- and four-spins entanglements. This field is narrowly connected with the one of solid-state spin qubits for quantum computation.

Publié le :
DOI : 10.1016/j.crhy.2005.10.003
Keywords: Nanomagnet, Molecule, Collective spin, Dynamics, Quantum, Tunnel, Rare-earths, Entanglement
Mot clés : Nanoaimant, Molécule, Spin collectif, Dynamique, Quantique, Tunnel, Terres Rares, Intrication
Bernard Barbara 1

1 Laboratoire Louis-Néel, CNRS, BP166, 38042 Grenoble cedex 09, France 
@article{CRPHYS_2005__6_9_934_0,
     author = {Bernard Barbara},
     title = {Quantum nanomagnet},
     journal = {Comptes Rendus. Physique},
     pages = {934--944},
     publisher = {Elsevier},
     volume = {6},
     number = {9},
     year = {2005},
     doi = {10.1016/j.crhy.2005.10.003},
     language = {en},
}
TY  - JOUR
AU  - Bernard Barbara
TI  - Quantum nanomagnet
JO  - Comptes Rendus. Physique
PY  - 2005
SP  - 934
EP  - 944
VL  - 6
IS  - 9
PB  - Elsevier
DO  - 10.1016/j.crhy.2005.10.003
LA  - en
ID  - CRPHYS_2005__6_9_934_0
ER  - 
%0 Journal Article
%A Bernard Barbara
%T Quantum nanomagnet
%J Comptes Rendus. Physique
%D 2005
%P 934-944
%V 6
%N 9
%I Elsevier
%R 10.1016/j.crhy.2005.10.003
%G en
%F CRPHYS_2005__6_9_934_0
Bernard Barbara. Quantum nanomagnet. Comptes Rendus. Physique, Volume 6 (2005) no. 9, pp. 934-944. doi : 10.1016/j.crhy.2005.10.003. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2005.10.003/

[1] L. Néel Ann. Geophys., 5 (1949), p. 99

[2] T. Lys Acta Cryst. B, 36 (1980), p. 2042

[3] R. Sessoli; D. Gatteschi; A. Caneschi; M.A. Novak Nature, 365 (1993), p. 141

[4] C. Paulsen; J.G. Park; B. Barbara; R. Sessoli; A. Caneschi; C. Paulsen; J.G. Park; B. Barbara; R. Sessoli; A. Caneschi J. Magn. Magn. Mater., 140–144 (1995), p. 379

[5] C. Paulsen; J.P. Park QTM'94, Chichilianne, France, NATO ASI Ser., Ser. E, vol. 301 (1995)

[6] B. Barbara et al. ICM'94, J. Magn. Magn. Mater., Volume 140–144 (1995), p. 1825

[7] L. Thomas; F. Lionti; R. Ballou; D. Gatteschi; R. Sessoli; B. Barbara Nature, 383 (1996), p. 145

[8] J.R. Friedman; M.P. Sarachik; J. Tejada; R. Ziolo Phys. Rev. Lett., 76 (1996), p. 20

[9] A.J. Leggett; A.J. Leggett QTM'94, Chichilianne, France, NATO ASI Ser., Ser. E, 69 (1980), p. 80

[10] M. Uehara; B. Barbara J. Phys. (Paris), 47 (1986), p. 235

[11] A.L. Barra; D. Gatteschi; R. Sessoli Phys. Rev. B, 56 (1996), p. 8192

[12] I. Chiorescu, Thesis Univ. J. Fourier, 2000, not published

[13] A. Garg Phys. Rev. Lett., 74 (1995), p. 1458

[14] W. Wernsdorfer; R. Sessoli Science, 284 (1999), p. 133

[15] J.L. van Hemmen; S. Suto Quantum Tunneling of Magnetization, NATO ASI Ser., Ser. E, vol. 301 (1995) Several authors developed analytical expressions for Δ. A very attracting one is given by, QTM'94, Chichilianne, France Starting from the Hamiltonian: H=−γSzl−(1/2)Σαn(S+n+S−n) where l=2,4,… is the order of longitudinal terms defining the barrier and 1⩽n⩽N the order of transverse terms allowing the splitting, they get a Universal expression for the tunnel splitting: Δ=(ℏlγσl−1/2)(αNσN/2γσl)2S/N which does not depend on the specific form of the barrier. This expression compares well with numerical results

[16] I. Chiorescu; R. Giraud; A. Jansen; A. Caneschi; B. Barbara Phys. Rev. Lett., 85 (2000), p. 4807

[17] L.D. Landau Phys. Z. Sowjetunion, 2 (1932), p. 46

[18] C. Zener Proc. R. Soc. London Ser. A, 137 (1932), p. 696

[19] E.C.G. Stückelberg Helv. Phys. Acta, 5 (1932), p. 369

[20] S. Miyashita J. Phys. Soc. Jpn., 64 (1995), p. 3207

[21] V.V. Dobrovitski; A.K. Zvezdin Europhys. Lett., 38 (1997), p. 377

[22] L. Gunther Europhys. Lett., 39 (1997), p. 1

[23] N.V. Prokof'ev; P.C.E. Stamp; N.V. Prokof'ev; P.C.E. Stamp QTM'94, Chichilianne, France, NATO ASI Ser., Ser. E, 5 (1993), p. L663

[24] I.S. Tupitsyn; N.V. Prokof'ev; P.C.E. Stamp Int. J. Mod. Phys. B, 11 (1997), p. 2901

[25] N.V. Prokof'ev; P.C.E. Stamp; N.V. Prokof'ev; P.C.E. Stamp; N.V. Prokof'ev; P.C.E. Stamp J. Low Temp. Phys., 80 (1998), p. 5794

[26] P.C.E. Stamp Tunneling in Complex Systems, Proceedings of the Institute for Nuclear Theory (S. Tomsovic, ed.), World Scientific, Singapore, 1998

[27] L. Thomas; B. Barbara; L. Thomas; A. Caneschi; B. Barbara Phys. Rev. Lett., 113 (1998), p. 1055

[28] N.V. Prokof'ev; P.C.E. Stamp Phys. Rev. Lett., 80 (1998), p. 5794

[29] W. Wernsdorfer; T. Ohm; C. Sangregorio; R. Sessoli; D. Mailly; C. Paulsen Phys. Rev. Lett., 82 (1999), p. 3903

[30] R. Giraud; W. Wernsdorfer; A.M. Tkachuk; D. Mailly; B. Barbara Phys. Rev. Lett., 87 (1991), p. 057203

[31] B. Barbara; R. Giraud; W. Wernsdorfer; D. Mailly; A.M. Tkachuk; P. Lejay; H. Susuki ICM'2003, Roma, JMMM, 272–276 (2004), p. 1024

[32] Sh.N. Gifeisman; A. Tkachuk; V. Prizmak; N.I. Agladze; M. Popova; N.I. Agladze; M. Popova Phys. Rev. Lett., 44 (1978), p. 68

[33] J. Magariño; J. Tuchendler; P. Beauvillain; I. Laursen Phys. Rev. B, 13 (1976), p. 2805

[34] R. Giraud; A.M. Tkachuk; B. Barbara Phys. Rev. Lett., 91 (2003) no. 25, p. 257204

[35] B. Barbara Nature, News & Views, 421 (2003), p. 32

[36] W. Wernsdorfer; W. Bhaduri; S. Tiron; R. Hendrickson; N. Christou Phys. Rev. Lett., 89 (2002), p. 197201

[37] N. Bloembergen et al. Phys. Rev., 114 (1959), p. 445

[38] P. Fazekas; P.W. Anderson Philos. Mag., 30 (1974), p. 423

[39] H.M. Rønnow; R. Parthasarathy; J. Jensen; G. Aeppli; T.F. Rosenbaum; D.F. McMorrow Science, 308 (2005), p. 389 (A first consequence of this work led to a reorientation of some spin-glass studies, taking now into account the role of nuclear spins)

[40] J. Villain; F. Hartmann-Bourtron; R. Sessoli; A. Rettori Europhys. Lett., 27 (1994), p. 159

[41] P. Politi; A. Rettori; F. Hartmann-Bourtron; J. Villain Phys. Rev. Lett., 75 (1995), p. 537

[42] F. Hartmann-Bourtron; P. Politi; J. Villain Int. J. Mod. Phys., 10 (1996), p. 2577

[43] M. Evangelisti; F. Luis; F.L. Mettes; N. Aliaga; G. Aromí; J.J. Alonso; G. Christou; L.J. de Jongh Phys. Rev. Lett., 93 (2004), p. 117202

[44] W. Wernsdorfer; E. Bonet Orozco; K. Hasselbach; A. Benoit; D. Mailly; O. Kubo; H. Nakano; B. Barbara Phys. Rev. Lett., 79 (1997), p. 20

[45] P.C.E. Stamp Elect. Proc. Int. Workshop “Quantum and Classical Spins Manipulations” (B. Barbara, ed.), Les Houches, France, 2005

Cité par Sources :

Commentaires - Politique

Ces articles pourraient vous intéresser

Quantum dynamics in molecular nanomagnets

Wolfgang Wernsdorfer

C. R. Chim (2008)

Resonance THz spectroscopy in high magnetic fields

Anne-Laure Barra; Michel Goiran; Roberta Sessoli; ...

C. R. Phys (2013)

Classical and quantum nonlinear phenomena in molecular magnetic clusters

Fernando Luis; Román López-Ruiz; Angel Millán; ...

C. R. Chim (2008)