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

ZERO MAGNETISATION SPIN-SOURCES 1 2 Spin-Hall effect in anti-ferromagnets Element-selective spin-emission 3 Spin-pumping from an anti-ferromagnet

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

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

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

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

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

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

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

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

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

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

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

3d-4f alloys

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

GdFeCo has a compensation temperature at which M=0 Temperature (K) 0 100 200 300 400 500 600 700 M(Gd) M(Fe) SiN(5nm) Pt(2nm) Gd25Fe65.6Co9.4(20nm) EASY AXIS Glass

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

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)

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

The mitted THz radiation is sensitive to the Fe spin only 𝐌𝟏 E=− M 1 B sin θ1 − M 2 B sin θ2 + J M 1 M 2 cos θ1+θ2 − − K 2 M 1 2 cos 2 θ − K 2 M 2 2 cos 2 φ 𝐌𝟐

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

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

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

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

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