3. Two magnetic states
Magnetism: TM ions
Ultimate Bit: MAE: 5d atoms
Our rationale
Stability: organic chemistry
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4. Magnetic in Bulk Phase
Nonmagnetic in
bulk, magnetic
at nanoscale
“THEORETICAL ENGINEERING”
Total Spin ~ 1-10
• Push up other multiplets to high energies
• Increase magnetic anisotropy
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5. 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 meV
To give a flavor: Record: TB in a Mollecular Magnet = 3K ;
Record TB in an inorganic nanostructure: 1.5 K in Co dimers
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6. EMAE Volume
EMAE = Edipolar + ESpin-Orbit
Edipolar >> ESpin-Orbit in bulk
EMAE Edipolar
Edipolar << ESpin-Orbit in nano
EBlocking
.
ESpin-Orbit Critical ~ 25 nm for Fe particles
10 nm for Co particles
Critical Volume V
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7. 5d
4d
3d
5s
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8. S,L S,L
d
1
E E|| EMAE
2
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9. 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, 205125
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10. Phys. Rev. B 75, 075415 (2007)
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11. See if reducing the number of TM atoms we
can understand things better
And try organic matrices:
Oscillating spin-density pattern in gold metallocene
phthalocyanines and metallocenes
and phthalocyanine molecules
Diego Carrascal, Lucas Fernández-Seivane, Jaime
Ferrer
Phys. Rev.
B, 80, 18, 184415 (2009); arXiv:0904.1138v1
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12. Spin ½ molecules
C
H N
Metallocenes (TMCp2) Phthalocyanines (TMPc)
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13. Cobalt Copper Gold
UNCONVENTIONAL MAGNETISM IN AuCp2
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17. 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
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18. 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)
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