Magnetoresistance in oxydized Ni nanocontacts

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Magnetoresistance in oxydized Ni nanocontacts
D. Jacob, J. Fernández-Rossier, J. J. Palacios
Department of Applied Physics, U. Alicante, 03690
SPAIN
Ni
Ni
Ni
Ni
Oxygen
Large Magnetoresistance gt90
Small Magnetoresistance
D. Jacob, JFR, J. J. Palacios PRB 71, R220403
(2005)
D. Jacob, JFR, J. J. Palacios Cond-mat, 0603359
A single atom can make a difference
www.ua.es/personal/jfrossier/
V22.00002
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Motivation I MR
EXPERIMENTSmall BMR in Ni80Fe20
K. Bolotin et al. Nano Lett., 6 (1), 123, (06)
D. Jacob, JFR J. J. Palacios PRB71, R220403
(2005)
THEORY Small BMR in PURE Ni nanocontacts
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Motivation II
Motivation III
Probing Ni-O-Ni chemical bond
Bulk NiOAF Mott Insulator
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Electronic Structure calculation
Ni
Ni
Oxygen
Tight Binding
B3LYP
Free Bands

• Parametrization 3D
• Charge neutrality

• Bulk NiO
• AF OK
• Insulator OK
• GAP Ok
• Magnetic Moment OK
• No Self Interaction OK

LDA

• NiO FM, no gap, no Mott Hubbard
• Self Interaction

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Electronic Structure calculation
Tight Binding
B3LYP
Free Bands

• Parametrization 3D
• Charge neutrality

• Bulk NiO
• AF OK
• Insulator OK
• GAP Ok
• Magnetic Moment OK
• No Self Interaction OK

LDA

• NiO FM, no gap, no Mott Hubbard
• Self Interaction

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Electronic Structure Infinite chains
CRYSTAL03
B3LYP, NiO FM chain
FERROMAGNETIC HALF METAL
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Doubly degenerate E1 band
Ni()O(-)
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Electronic Structure Infinite chains
CRYSTAL03
B3LYP, NiO AF chain
ANTIFERROMAGNETIC INSULATING
Ni()O(-)
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Electronic structure nanocontact

• Infinite system without translational invariance
• Cluster Embedded calculation
• Cluster in DFT aprox, LCAO, GAUSSIAN03
• Leads semiempirical TB, Bethe lattice

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Nanocontacts Single Oxygen Bridge
High MR
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Electronic Structure Infinite chains
FERROMAGNETIC INSULATING
WARNING Small MR
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SINGLE ATOM SPIN VALVE
Ni
Ni
Ni
Conducting
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Conclusions

• A single atom can make a difference Ni-O-Ni can
  have large MR
• A single atom can makes a differenceSINGLE ATOM
  SPIN VALVE
• Atomic sized contacts PROBING TM-O-TM chemical
  bonding

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