18. jan 2011 C. M. Schneider
Peter Grünberg Institut PGI–6 “Electronic Properties”
Perspectives in Spintronics:
Research @ PGI–6 / NanoSync
Mitglied der Helmholtz-Gemeinschaft
PGI–6 “Electronic Properties”
©MS 2012
challenges in nanomagnetism
2
lateral nano- structures
chemical/magnetic complexity
fast/ultrafast phenomena
magnetism and
spintransport on the
nanoscale
spin
coherence
& transport
precessional motion
ultrafast phase transitions
Ta
NiFe CoFe Cu CoFe IrMn
Ta SiO2 Cu
transition metal oxides
thin film systems
endohedral fullerenes in carbon nanotubes spin electronics
magnetic nanostructures magnetic molecules
• lateral resolution
• energy resolution
• time resolution
• information depth
•
PGI–6 “Electronic Properties”
©MS 2012
Scientific topics (selection)
Spin-filter tunneling barriers
Topological insulators
Spin-transfer torque dynamics
Ultrafast spin dynamics
Resistive oxides (➨ R. Waser)
Spectronanoscopy development
3
PGI–6 “Electronic Properties”
©MS 2012
Magnetic Oxides @ PGI-6
~100% Spin Filter
Europium Oxide
Nickel Ferrite
Low-T C model system
… on Silicon
functional MO/silicon hybrid
High-T C spin filter (HTSF)
… thin films
Sizable SF
efficiency at RT
4
PGI–6 “Electronic Properties”
©MS 2012
Magnetic Oxides I: Europium Oxide/Si
sample
Physical Review B 84, 205206 (2011) Phys. Status Solidi RRL 5, 441 (2011)
EuO/Si interface control
EuO bulk chemistry
HAXPES: High-energy
photoemission spectroscopic bulk probe
Epitaxy by Oxide-MBE
5
PGI–6 “Electronic Properties”
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Topological insulator: Bi 2 Te 3 thin films
two-dimensional semiconductor
Dirac-like dispersion
interesting for spintronic applications
6
20nm --->>--->>--- 1nm
PGI–6 “Electronic Properties”
©MS 2012
Angle- and spin resolved PES on TIs
7
• Dirac cones in thin films
• Fermi level lies either within the CB or VB (no insulating state in bulk)
• Large ESP for in-plane component and non-zero ESP for out-of-plane,
• Reversal of ESP for two mirror symmetric points (A and B) ➨ single domain surface (no 60°
inverted domains), or one
dominant domain.
Spin-torque dynamics of stacked vortices in magnetic nanopillars
Spin-transfer torque (STT) in double vortex state:
• Controlled preparation of of 16 chirality/polarity combinations
• STT-induced dynamics of gyrotropic vortex dynamics
• Non-linear oscillator dynamics of coupled vortices
• Injection locking of vortex dynamics as prerequisite to oscillator synchronization
V. Sluka, A. Kakay, A.M. Deac, D.E. Bürgler, R. Hertel and C.M. Schneider, submitted (2011)
DC and HF transport experiments
Micromagnetic
simulations
Current polarity determines the excited disk and thus the excitation frequency
Possibility to switch the oscillator between two well-separated frequency bands
Experiment Simulation
Core-core interaction lifts the degeneracy of the coupled vortex dynamics
Possibility to read-out the polarization state for memory applications
V. Sluka, A. Kakay, A.M. Deac, D.E. Bürgler, R. Hertel and C.M. Schneider, submitted (2011)
Spin-torque dynamics of stacked vortices in magnetic nanopillars
PGI-6 “Electronic Properties”
©MS 2011 XRMS’11, Stanford, Oct. 2011
HHG set-up: ultrashort pulsed VUV source
10
IR Pump (780 nm)
CCD
camera
PGI–6 “Electronic Properties”
©MS 2012
evolution of asymmetry during demagnetization
11
Movie of asymmetry signal decay in Ni and Fe after fs-laser excitation
PGI–6 “Electronic Properties”
©MS 2012
Cu-doped Permalloy
12
Permalloy-Cu: Δ Fe, Ni = 80 fs
• Reduce the exchange coupling strength by alloying Cu into the Permalloy.
• Reduce in exchange coupling increase in decoupling
• Possible interpretation:
! “Ultrafast breakdown of exchange
! interaction”?
Fluence-dependent measurements Permalloy: Δ Fe, Ni = 20 fs
R e d u ce d Exch a n g e
-0.2 0 0.2 0.4 0.6 0.8 1
0.2 0.4 0.6 0.8 1
-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6
0.1 1
!
!"#Asymme try A/ A
0!N o rma lize d Asymme try C h a n g e s D A !
b!
!
!$%&'(#!
!$%)*#Delay
!Permalloy-Cu !
-0.2 0 0.2 0.4 0.6 0.8 1
0.7 0.8 0.9 1
Time Delay (ps)!
Asymme try A/ A
0!a!
Fe!
Ni!
Permalloy !
Fe!
Ni!
Freitag, 20. Januar 2012
elliptical undulator, var. pol., 50 - 1500 eV
planar undulator
lin. pol., 10 - 400 eV planar undulator
lin. pol. 200 - 1000 eV 1 sector, 4 experiments
2 - 150 keV
NanoESCA
var. pol., 50 - 1000 eV
JSRL
Dortmund, Germany Dortmund, Germany
Trieste, Italy
Berlin, Germany
Argonne,
USA
15. September 2011 Folie 8
Energy-filtered PEEM imaging at core levels
800 600 400 200 0
0 1000 2000 3000 4000
Au4p
AuVB Au4d
Intensity [a.u.]
Ebin[eV]
NanoESCA:
1mm slits, 100eV passenergy Sample: Chessy
h! = 4900eV
Au4f
Si2p
105 100 95 90 85 80 75
0 1000 2000 3000 4000 5000
SiOx
Intensity [a.u.]
Ebin[eV]
NanoESCA:
1mm slits, 100eV passenergy Sample: Chessy
h! = 6500eV
Au4f
Si
Au 4f
7/2Si1s
PGI “Electronic Properties”
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imaging HAXPES in the NanoESCA @ PETRA III
14
Aug. 2011
PGI “Electronic Properties”
©MS 2011
information depth
15
sample: SrTiO 3 with Au top electrode
lateral resolution: ~400 nm at present
PGI–6 “Electronic Properties”
©MS 2012
acknowledgment
16
PGI–6 “Electronic Properties”
©MS 2012 17
