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Ismanam 2011 fernandez seivane
 

Ismanam 2011 fernandez seivane

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    Ismanam 2011 fernandez seivane Ismanam 2011 fernandez seivane Presentation Transcript

    • http://sites.google.com/site/quevedin/Jaime Ferrer Diego Carrascal Víctor García Suárez
    • Huge Magnetic Anisotropy in Nanostructures 1/07/2011 4
    • Two magnetic statesMagnetism: TM ions Ultimate Bit: MAE: 5d atoms Our rationale Stability: organic chemistry Huge Magnetic Anisotropy in Nanostructures 1/07/2011 5
    • Magnetic in Bulk PhaseNonmagnetic inbulk, magnetic at nanoscale “THEORETICAL ENGINEERING” Total Spin ~ 1-10 • Push up other multiplets to high energies • Increase magnetic anisotropy Huge Magnetic Anisotropy in Nanostructures 1/07/2011 6
    • EMAE t/τ EMAE / KT M = M 0e τ = 10 7 e sec Time requirements for a τ = 1012 seconds bit EMAE,Critical = EBlocking 50 KTB Blocking Temperature Set T B = 300 K E Blocking = 1300 meVTo give a flavor: Record: TB in a Mollecular Magnet = 3K ;Record TB in an inorganic nanostructure: 1.5 K in Co dimers Huge Magnetic Anisotropy in Nanostructures 1/07/2011 8
    • EMAE Volume EMAE = Edipolar + ESpin-Orbit Edipolar >> ESpin-Orbit in bulk EMAE Edipolar Edipolar << ESpin-Orbit in nanoEBlocking . ESpin-Orbit Critical ~ 25 nm for Fe particles 10 nm for Co particles Critical Volume V Huge Magnetic Anisotropy in Nanostructures 1/07/2011 9
    • 5d 4d 3d 5sHuge Magnetic Anisotropy in Nanostructures 1/07/2011 10
    • S,L S,L d 1 E E|| EMAE 2 Huge Magnetic Anisotropy in Nanostructures 1/07/2011 11
    • Phys. Rev. Lett. 99, 183401 (2007) Phys. Rev. Lett. 101, 069903(E) (2008) Pt2: ground state parallel to the axis, Anisotropy of ~ 100 meV, S=1 Ir2: ground state parallel to the axis, Anisotropy of ~ 60 meV, S=2, some changes in the spin with the distance Pd2: ground state perpendicular to the axis, tiny Anisotropy ~ 5 meV, S=1, sudden jump in L a bit above the equilibrium distance Au2: ground state in singlet, L=0, S=0. Many of this, or very similar results, have been confirmed indepently and by different methods by other groups, for instance Piotr Błoński and Jürgen Hafner 2011 J. Phys.: Condens. Matter 23, 136001 or Ruijuan Xiao, Daniel Fritsch et al., Phys Rev. B 82, 205125Huge Magnetic Anisotropy in Nanostructures 1/07/2011 13
    • Phys. Rev. B 75, 075415 (2007)Huge Magnetic Anisotropy in Nanostructures 1/07/2011 15
    •  See if reducing the number of TM atoms we can understand things better And try organic matrices: Oscillating spin-density pattern in gold metallocenephthalocyanines and metallocenes and phthalocyanine molecules Diego Carrascal, Lucas Fernández-Seivane, Jaime Ferrer Phys. Rev. B, 80, 18, 184415 (2009); arXiv:0904.1138v1 Huge Magnetic Anisotropy in Nanostructures 1/07/2011 16
    • Spin ½ molecules C H NMetallocenes (TMCp2) Phthalocyanines (TMPc) Huge Magnetic Anisotropy in Nanostructures 1/07/2011 17
    • Cobalt Copper Gold UNCONVENTIONAL MAGNETISM IN AuCp2 Huge Magnetic Anisotropy in Nanostructures 1/07/2011 18
    • Huge Magnetic Anisotropy in Nanostructures 1/07/2011 19
    • Cobalt Copper Gold UNCONVENTIONAL MAGNETISM IN AuPc Phys. Rev. B, 80, 18, 184415 (2009) arXiv:0904.1138v1 Huge Magnetic Anisotropy in Nanostructures 1/07/2011 20
    • Huge Magnetic Anisotropy in Nanostructures 1/07/2011 21
    •  Look for molecules containing 5d elements → large SO interaction Unconventional magnetism in gold organometallic molecules Most molecules have S=0 or ½ A few Alkene-based molecules had a higher spin and MAE ~ 10 meV Failure to find huge magnetic anisotropies Huge Magnetic Anisotropy in Nanostructures 1/07/2011 23
    • SIESTA The Siesta method; developments and applicability. E. Artacho, E. Anglada, et al. J. Phys.: Condens. Matter 20, 064208 (2008).SIESTA+SO On-site approximation for spin-orbit coupling in LCAO density functional methods. L. Fernandez-Seivane, M. A. Oliveira, S. Sanvito, J. Ferrer, J. Phys. : Condens. Matter 18 7999 (2006); arxiv:cond-mat/0601093 Predictions for the formation of new atomic chains in Mechanically Controllable Break Junction experiments L. Fernandez-Seivane, V. M. Garcia-Suarez, J. Ferrer Phys. Rev. B 75, 075415 (2007); arXiv:cond mat/0611624v1 Magnetic anisotropies of late transition metal atomic clusters Lucas Fernández-Seivane, Jaime Ferrer Phys. Rev. Lett. 99, 183401 (2007); arXiv:cond-mat/0610879v2 Oscillating spin-density pattern in gold metallocene and phthalocyanine molecules Diego Carrascal, Lucas Fernández-Seivane, Jaime Ferrer Phys. Rev. B, 80, 18, 184415 (2009); arXiv:0904.1138v1 Magnetic properties of small Pt-capped Fe, Co, and Ni clusters: A density functional theory study Sahoo, S.; Hucht, A.; Gruner, M. E.; et al. Phys. Rev. B 82, 054418 (2010); arxviv:0907.2678 Magnetic properties of Fe-2n and (FePt)(n) (n <= 5) clusters and magnetic anisotropy of transition metal dimers Boufala, K.; Fernandez-Seivane, L.; Ferrer, J.; et al. Journal of Magnetism and Magnetic Materials, 322, 21 Pages:3428-3437 (2010) Huge Magnetic Anisotropy in Nanostructures 1/07/2011 24
    • Huge Magnetic Anisotropy in Nanostructures 1/07/2011 25