1. ZERO-MAGNETISATION SPIN-SOURCES
Chiara Ciccarelli
University of Cambridge
ZERO-MAGNETISATION SPIN-SOURCES
SPICE workshop on anti-ferromagnetic spintronics
26-30 September 2016

2. ZERO MAGNETISATION SPIN-SOURCES1 2
Spin-Hall effect in anti-ferromagnets
Element-selective spin-emission 3
Spin-pumping from an anti-ferromagnet

3. The Spin-Hall effect in anti-ferromagnets
EXPERIMENT 1
The Spin-Hall effect in anti-ferromagnets

4. We determine the current-induced fields by FMR𝐦 θ B
NiFe (4 nm)
IrMn (4 nm) x y z
Seed layer

5. We determine the current-induced fields by FMR
Vdc 𝐦 θ B
V t =R ωt ×I ωt =
= V dc +V(2ωt)
NiFe (4 nm)
IrMn (4 nm) x y z
Seed layer
Tulapurkar, Nature 2005
Fang, Nature Nano 2011

6. We determine the current-induced fields by FMR
Vdc 𝐦 θ B hy
𝐡 𝐳 ~𝛔×𝐦
NiFe (4 nm) hz
IrMn (4 nm) x y z
Seed layer
@ 107 A/cm2 hz
1.13∓0.05 mT hy
1.04∓0.03 mT
hOe
1.09∓0.07 mT
Tshitoyan, PRB 2015

7. SHE-STT or ELSE? NiFe (4 nm) Cu (2 nm) IrMn (4 nm) seed qSH = 5.6 %
qSH(Ir20Mn80)∼0.8qSH(Pt) Mendes, 2014
q(Ir50Mn50) ∼2% Zhang, 2014
Tshitoyan, PRB 2015

8. SHE-STT or ELSE? NiFe (4 nm) Cu (2 nm) IrMn (4 nm) qSH = 22 % seed
Tshitoyan, PRB 2015

9. The SH angle is correlated to the exchange field
qSH = 22 %
Tshitoyan, PRB 2015

10. Coupled dynamics might be at the origin of the increase in hz
μ 0 𝛻H ω = μ 0 𝛻H inh + α eff ω γ
Tshitoyan, PRB 2015

11. We get a negative value of Gmix
Coupled dynamics might be at the origin of the increase in hz
μ 0 𝛻H ω = μ 0 𝛻H inh + α eff ω γ
We get a negative value of Gmix
Unphysical
α eff = α sp + α ex
Tserkovnyak, PRB 2002
Tshitoyan, PRB 2015

12. Element-selective spin emission from a ferrimagnet
EXPERIMENT 2
Element-selective spin emission from a ferrimagnet

13. Ultra-fast spin emission in magnetic bilayers
In this case the emitted spin current is aligned with the net magnetisation.
Is it possible to have zero-magnetisation spintronic emitters of THz radiation?
T. Seifert et al., Nature Photonics 2016
T. Kampfrath et al., Nature Nanotech. 2013

14. 3d-4f alloys

15. 3d-4f alloys
C.D. Stanciu et al., PRB 2006
J. Becker, PhD thesis, 2016

16. GdFeCo has a compensation temperature at which M=0
Temperature (K)
M(Gd)
M(Fe)
SiN(5nm)
Pt(2nm)
Gd25Fe65.6Co9.4(20nm)
EASY AXIS
Glass

17. We use THz emission spectroscopy to measure spin-emission
E(t)≈ σ ip (t)× z z
800 nm
50 fs

18. The mitted THz radiation has the symmetry of the ISHE
ROOM TEMPERATURE B B B B
𝛔 𝐢𝐩 (𝐭)
𝛔 𝐢𝐩 (𝐭)
𝛔 𝐢𝐩 (𝐭)
𝛔 𝐢𝐩 (𝐭)

19. The mitted THz radiation is sensitive to the Fe spin only
BELOW Tcomp B Gd Fe
ABOVE Tcomp B Fe Gd

20. The mitted THz radiation is sensitive to the Fe spin only𝐌𝟏
E=− M 1 B sin θ1 − M 2 B sin θ2 + J M 1 M 2 cos θ1+θ2 −
− K 2 M cos 2 θ − K 2 M cos 2 φ 𝐌𝟐

21. Spin-pumping from anti-ferromagnets
EXPERIMENT 3
Spin-pumping from anti-ferromagnets

22. Spin-pumping from an AFM
FERROMAGNETS
ANTI-FERROMAGNETS
R. Cheng et al., PRL 2014

23. Spin-pumping from an AFM
100
010
001
KNiF3
TN=246 K
Eg=6.2 eV
D. Bossini et al., PRB 2014
FERROMAGNETS
ANTI-FERROMAGNETS
R. Cheng et al., PRL 2014

24. Spin-pumping from an AFM
FERROMAGNETS
ANTI-FERROMAGNETS
R. Cheng et al., PRL 2014
D. Bossini et al., PRB 2014

25. SUMMARY 1 2 3 Nijmegen Leeds Prague Alexey Kimel Tom Moore
Spin-Hall effect in anti-ferromagnets
Element-selective spin-emission
Cambridge
Vahe Tshytoyan
Andrew Irvine
Andrew Ferguson
Nijmegen
Alexey Kimel
Thomas Huisman
Rostislav Mikhaylovskiy
Theo Rasing
Leeds
Tom Moore
Andrei Mihai,
Mannan Ali
Prague
Tomas Jungwirth 3
Spin-pumping from an anti-ferromagnet
Leeds
Tom Moore
Rowan Temple
Chris Marrows
Nijmegen
Alexey Kimel
Thomas Huisman
Rostislav Mikhaylovskiy
Theo Rasing
University of Tokyo
Davide Bossini
Prague
Zbynek Soban
Tomas Jungwirth
Nottingham
Andrew Rushforth
Bryan Gallagher