Takahiro Moriyama

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Presentation 2 for ELEG 667
GMR in p-conjugated organic semiconductor barrier
Takahiro Moriyama
Citation Z. H. Xiong et al, Nature 247, 821(2004)
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Spintronics in inorganic materials
Magnet Fe, Ni, Co, Gd, Mn Non-Magnet Cu, Cr,
Al Insulator Al2O3, MgO Semiconductor Si,
GaAs
Or alloys
Spintronics in organic materials
Combination of C, O, H, Cl, S, N and so on.
Almost unlimited!!
Magnetic material Insulator Semiconductor Conducto
r
You can make
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Whats the p-conjugated organic semiconductor ?
e-
8-hydroxy-quinoline aluminum
band structure
Band gap
LUMO Lowest unoccupied molecular orbit?
Conduction band
HOMO highest occupied molecular orbit ? Valence
band
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Why p-conjugated organic semiconductor ?
There is no d-orbit involved.
long spin diffusion length.
Due to extremely weak spin-orbit interaction.
? Suitable for spin injection materials.
Typical p-conjugated organic semiconductors
Alq3 8-hydroxy-quinoline aluminum
PPV Poly2-methoxy-5-(2'-ethylhexyloxy)- 1,4-ph
enylenevinylene
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Experimental procedure
Z. H. Xiong et al, Nature 247, 821(2004)
2X3mm2
Hole injection
Alq3 8-hydroxy-quinoline aluminum
LSMO(LaSrMnO) half metal at low temperature
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result
LSMO(100nm)/Alq3(130nm)/Co(3.5nm)
J.M. De Teresa, et al Science 286, 507(1999)
Negative TMR ? negative spin polarization of Co
d-band
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result
Thickness dependence of GMR
Inter layer is very thick
Spin diffusion length 45nm
Parkin, et al PRL 64 2304(1990)
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Conclusion
Spin injection, transport and detection can be
successfully achieved using pi- conjugated OSE
Easy fabrication process from industrial point of
view
Application
Spin injection device with organic
semiconductor Magnetic organic LED
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Magnetic LED
LUMO
hn
Mag.
HOMO
Mag.
anode
cathode
Electric dipole selection rule
Singlet S0, ms0
Triplet S1, ms-1,0,1
_

50 efficient (magnetically switch)
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Metal Spintronics
inorganic semiconductors spintronics
Organic semiconductor spintronics