Magnetoresistance in oxydized Ni nanocontacts

Department of Applied Physics, U. Alicante, 03690 SPAIND. Jacob, J. Fernández-Rossier, J. J. Palacios

www.ua.es/personal/jfrossier/ V22.00002

Ni Ni

Oxygen

Large Magnetoresistance>90%

Small Magnetoresistance

Ni Ni

A single atom can make a difference

D. Jacob, JFR, J. J. Palacios

PRB 71, R220403 (2005)

D. Jacob, JFR, J. J. Palacios

Cond-mat, 0603359

Motivation I: MR

K. Bolotin et al. Nano Lett., 6 (1), 123, (06)

EXPERIMENT:Small BMR in Ni80Fe20

THEORY: Small BMR in PURE Ni nanocontacts

D. Jacob, JFR; J. J. Palacios

PRB71, R220403 (2005)

Bulk NiO=AF Mott Insulator

Ni Ni

Oxigen

Motivation II:

Motivation III:

Probing Ni-O-Ni chemical bond

Electronic Structure calculation

Ni Ni

Oxygen

Free BandsTight Binding

LDA

B3LYP

•Parametrization 3D•Charge neutrality

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

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

n

Fn EThe

G )(2

Electronic Structure calculation

Ni Ni

Oxigen

Free BandsTight Binding

LDA

B3LYP

•Parametrization 3D•Charge neutrality

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

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

n

Fn EThe

G )(2

Electronic Structure: Infinite chains

FERROMAGNETICHALF METAL

Doubly degenerate E1 band2

B3LYP, NiO FM chain

CRYSTAL03

Ni(+)O(-)

Electronic Structure: Infinite chains

ANTIFERROMAGNETIC

INSULATING

CRYSTAL03

B3LYP, NiO AF chain

Ni(+)O(-)

Electronic structure: nanocontact

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

)(1

)(EHE

EG

GGET )(

Ni Ni

Oxigen

Nanocontacts: Single Oxygen Bridge

High MR

he

GP

22

he

GDW

221.0

10DW

P

GG

Electronic Structure: Infinite chains

FERROMAGNETICINSULATING

WARNING:Small MR

Ni Ni

SINGLE ATOM SPIN VALVE

Ni

Conducting Insulating

10DW

P

GG

Conclusions

• A single atom can make a difference: Ni-O-Ni can have large MR

• A single atom can makes a difference:SINGLE ATOM SPIN VALVE

• Atomic sized contacts: PROBING TM-O-TM chemical bonding

www.ua.es/personal/jfrossier

Jfrossier@ua.es