Spin Hall effect in heavy metals mechanisms and

Spin Hall effect in heavy metals: mechanisms and optimization XXXVI Reunión Bienal de la RSEF Santiago de Compostela, July 17 th 2017 Fèlix Casanova Nanodevices group, CIC nano. GUNE San Sebastian, Basque Country (Spain)

OUTLINE Spin-orbitronics 20/02/2021 Spin Hall effect in Pt: mechanisms XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu Spin-to-charge conversion: optimization 2

OUTLINE Spin-orbitronics 20/02/2021 Spin Hall effect in Pt: mechanisms XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu Spin-to-charge conversion: optimization 3

INTRODUCTION: spin-orbitronics Spin-orbit coupling: 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 4

INTRODUCTION: spin-orbitronics The art of manipulating the spin with spin-orbit coupling Spin-tocharge conversion A. Fert et al. , Nature Nanotech. 8, 152 (2013) Spin Hall effect (3 D) Edelstein effect (2 D) SPIN ORBITRONICS Skyrmions Spin transistor S. Datta and B. Das, Appl. Phys. Lett. 56, 665 (199 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 5

INTRODUCTION: spin-to-charge current conversion ANOMALOUS HALL EFFECT in a FM material SPIN HALL EFFECT in a NM material H V ü Spin-orbit coupling E. H. Hall, Phil. Mag. 12, 157 (1881) R. Karplus and J. M. Luttinger, Phys. Rev. 95, 1154 (1954) 20/02/2021 ü Spin-orbit coupling M. I. Dyakonov & V. I. Perel, JETP Lett. 13, 467 (1971) Y. Kato et al. , Science 306, 1910 (2004) S. Valenzuela et al. , Nature 442, 176 (2006) XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 6

INTRODUCTION: spin-to-charge current conversion Direct effect (SHE) Inverse effect (ISHE) Js Jc Js θSH Jc Spin current generation 20/02/2021 Jc Js Spin current detection XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 7

INTRODUCTION: phenomena and applications Spin Seebeck effect Uchida et al. , Nature Mater. 9, 894 (2010) Spin pumping Zutic et al. , Nature Mater. 10, 647 (2011) Spin-orbit torques Miron et al. , Nature 476, 189 (2011) Pai et al. , Science 336, 555 (2012) 20/02/2021 Spin Hall magnetoresistance Nakayama et al. , PRL 110, 206601 (2013) Spin-orbit logic Manipatruni et al. , ar. Xiv: 1512. 05428 (2015) XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 8

OUTLINE Spin orbitronics 20/02/2021 Spin Hall effect in Pt: mechanisms XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu Spin-to-charge conversion: optimization 9

SPIN HALL EFFECT in Pt: overview • Large dispersion in literature • Mechanism of the SHE ? Intrinsic Skew scattering Band structure Spin-dependent scattering at impurities • Optimization of spin Hall angle ? J. Sinova et al. , Rev. Mod. Phys 87, 1213 (2015) 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 10

SPIN HALL EFFECT in Pt: spin absorption Spin absorption measurement H V I M M NM TM FM Injector Is I´s FM TM Py/Cu Detector Useful for short spin diffusion lengths TM is a crucial parameter for a proper quantification of θSH !! M. Isasa et al. , Phys. Rev. B 91, 024402 (2015) M. Morota et al. , Phys. Rev. B 83, 174405 (2011) E. Sagasta et al. , Phys. Rev. B 94, 060412(R) (2016) P. Laczkowski et al. , Appl. Phys. Lett. 104, 142403 (2014) 11 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu

SPIN HALL EFFECT in Pt: spin absorption V • Pt wires with different resistivity (evaporated vs sputtered) • Different temperatures I Cu Pt I V Py H 1 m Elliott-Yafet dominates spin relaxation in Pt M. Isasa et al. , Phys. Rev. B 91, 024402 (2015) E. Sagasta et al. , Phys. Rev. B 94, 060412(R) (2016) 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 12

SPIN HALL EFFECT in Pt: spin absorption z H I Is M NM y x Ic V Is F M TM F M 2 DRSCC M. Isasa et al. , Phys. Rev. B 91, 024402 (2015) M. Morota et al. , Phys. Rev. B 83, 174405 (2011) E. Sagasta et al. , Phys. Rev. B 94, 060412(R) (2016) P. Laczkowski et al. , Appl. Phys. Lett. 104, 142403 (2014) 13 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu

SPIN HALL EFFECT in Pt: results V I Pt H Cu Temperature evolution of the SHE enables to determine SHE contributions (following AHE relation): Tian et al. , Phys. Rev. Lett. 103, 087206 (2009) Py 20/02/2021 1 μm E. Sagasta et al. , Phys. Rev. B 94, 060412(R) (2016) XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 14

SPIN HALL EFFECT in Pt: results device E 1 6. 66 10. 1± 0. 1 2. 1± 0. 7 1480± 110 1. 2± 0. 2 E 2 6. 66 10. 1± 0. 1 1. 7± 0. 4 1780± 95 0. 7± 0. 2 E 3 9. 42 6. 7± 0. 1 2. 2± 0. 2 1750± 360 0. 4± 0. 5 E 4 10. 12 6. 5± 0. 1 2. 2± 0. 3 1910± 700 0. 1± 0. 9 S 1 44. 19 0. 75± 0. 03 8. 5± 1. 3 1525± 220 2. 1+1. 3 S 2 44. 19 0. 75± 0. 03 7. 4± 0. 7 1280± 140 2. 0± 0. 9 S 3 24. 96 3. 43± 0. 05 5. 3± 0. 6 1435± 390 1. 9± 1. 4 S 4 56. 25 0. 59± 0. 01 10. 7± 1. 0 1770± 760 1. 6± 5. 2 Theory: T. Tanaka et al. , Phys. Rev. B 77, 165117 (2008) L. Wang et al. , Phys. Rev. Lett. 116, 196602 (2016) Skew scattering angle slightly different Intrinsic spin Hall conductivity is constant E. Sagasta et al. , Phys. Rev. B 94, 060412(R) (2016) 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 15

SPIN HALL EFFECT in Pt: results INTRINSIC EXTRINSIC Moderately dirty Superclean metal (Sputtered) (Evaporated) SHE Crossover between the moderately dirty and the superclean scaling regimes of the SHE AHE ü Large dispersion in literature ü Mechanism of the SHE ü Optimization of spin Hall angle Onoda et al. , Phys. Rev. B 77, 165103 (2008) 20/02/2021 E. Sagasta et al. , Phys. Rev. B 94, 060412(R) (2016) XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 16

OUTLINE Spin orbitronics 20/02/2021 Spin Hall effect in Pt: mechanisms XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu Spin-to-charge conversion: optimization 17

OPTIMIZATION: increasing resistivity INTRINSIC EXTRINSIC Moderately dirty. Superclean metal (Sputtered) (Evaporated) ü Larger θSH in metals with intrinsic mechanism ü Larger voltage drop for the same θSH ✗ More shunting K. Fujiwara et al. , Nature Comms. 4, 2893 (2013) 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 18

OPTIMIZATION: avoiding shunting effects Graphene Ic Is Co Pt V By Y. Omori et al. , APL 104, 242415 (2014) 20/02/2021 W. Yan et al. , ar. Xiv: 1702. 01971 (accepted in Nature XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 19

SUMMARY INTRINSIC EXTRINSIC Moderately dirty Superclean metal (Sputtered) (Evaporated) 1. Spin Hall effect in Pt • • • Intrinsic spin Hall conductivity of 1600 -1 cm-1 Moderately dirty and superclean regimes in SHE Path to enhance spin Hall angle by increasing resistivity M. Isasa et al. , Phys. Rev. B 91, 024402 (2015) E. Sagasta et al. , Phys. Rev. B 94, 060412(R) (2016) 2. Optimization of spin-to-charge conversion • • Higher resistivity of SHE metal not useful due to shunting Large spin-to-charge conversion at RT using graphene Ic W. Yan et al. , ar. Xiv: 1702. 01971 (accepted in Nature Comms. ) Is Co Pt V By 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 20

ACKNOWLEDGMENTS ISSP (U. Tokyo) Nanodevices group W. Yan E. Villamor L. E. Hueso E. Sagasta M. Isasa Y. Omori Osaka University Y. Niimi Y. Otani University of Bristol M. Gradhand FUNDING: 20/02/2021 XXXVI Reunión Bienal de la RSEF f. casanova@nanogune. eu 21