Spintronic terahertz (THz) emitters based on the inverse spin Hall effect in ferromagnetic/heavy metal (FM/HM) heterostructures have become important sources for THz pulse generation. The design, materials, and control of these interfaces at the nanometer level have become vital to engineer their THz emission properties. In this work, we present studies of the optimization of such structures through a multi-pronged approach, taking advantage of material and interface engineering to enhance THz spintronic emission. This includes the application of multi-stacks of HM/FM junctions and their application to trilayer structures, the use of spin-sinks to simultaneously enhance the THz emitted fields and reduce the use of thick Pt layers to reduce optical absorption, and the use of semi-metals to increase the spin polarization and, thus, THz emission. Through these approaches, significant enhancements of the THz field can be achieved. Importantly, taking into account the optical absorption permits to elucidate novel phenomena such as the relation between the spin diffusion length and the spin-sink using THz spectroscopy, as well as possibly distinguishing between self- and interface-spin-to-charge conversion in semi-metals.
References
1.
T.
Seifert
, S.
Jaiswal
, U.
Martens
, J.
Hannegan
, L.
Braun
, P.
Maldonado
, F.
Freimuth
, A.
Kronenberg
, J.
Henrizi
, I.
Radu
, E.
Beaurepaire
, Y.
Mokrousov
, P. M.
Oppeneer
, M.
Jourdan
, G.
Jakob
, D.
Turchinovich
, L. M.
Hayden
, M.
Wolf
, M.
Münzenberg
, M.
Kläui
, and T.
Kampfrath
, “Efficient metallic spintronic emitters of ultrabroadband terahertz radiation
,” Nat. Photonics
10
, 483
–488
(2016
).2.
C.
Bull
, S. M.
Hewett
, R.
Ji
, C.-H.
Lin
, T.
Thomson
, D. M.
Graham
, and P. W.
Nutter
, “Spintronic terahertz emitters: Status and prospects from a materials perspective
,” APL Mater.
9
(9
), 090701
(2021
).3.
L.
Cheng
, Z.
Li
, D.
Zhao
, and E. E. M.
Chia
, “Studying spin-charge conversion using terahertz pulses
,” APL Mater.
9
(7
), 070902
(2021
).4.
E. T.
Papaioannou
and R.
Beigang
, “THz spintronic emitters: A review on achievements and future challenges
,” Nanophotonics
10
(4
), 1243
–1257
(2021
).5.
M.
Battiato
, K.
Carva
, and P. M.
Oppeneer
, “Superdiffusive spin transport as a mechanism of ultrafast demagnetization
,” Phys. Rev. Lett
105
, 027203
(2010
).6.
M.
Battiato
, K.
Carva
, and P. M.
Oppeneer
, “Theory of laser-induced ultrafast superdiffusive spin transport in layered heterostructures
,” Phys. Rev. B
86
, 024404
(2012
).7.
L.
Cheng
, X.
Wang
, W.
Yang
, J.
Chai
, M.
Yang
, M.
Chen
, Y.
Wu
, X.
Chen
, D.
Chi
, K. E. J.
Goh
, J.-X.
Zhu
, H.
Sun
, S.
Wang
, J. C. W.
Song
, M.
Battiato
, H.
Yang
, and E. E. M.
Chia
, “Far out-of-equilibrium spin populations trigger giant spin injection into atomically thin MoS2
,” Nat. Phys.
15
, 347
–351
(2019
).8.
D.
Yagodkin
, L.
Nádvorník
, O.
Gueckstock
, C.
Gahl
, T.
Kampfrath
, and K. I.
Bolotin
, “Ultrafast photocurrents in MoSe2 probed by terahertz spectroscopy
,” 2D Mater.
8
, 025012
(2021
).9.
R.
Adam
, G.
Chen
, D. E.
Bürgler
, T.
Shou
, I.
Komissarov
, S.
Heidtfeld
, H.
Hardtdegen
, M.
Mikulics
, C. M.
Schneider
, and R.
Sobolewski
, “Magnetically and optically tunable terahertz radiation from Ta/NiFe/Pt spintronic nanolayers generated by femtosecond laser pulses
,” Appl. Phys. Lett.
114
(21
), 212405
(2019
).10.
R. I.
Herapath
, S. M.
Hornett
, T. S.
Seifert
, G.
Jakob
, M.
Kläui
, J.
Bertolotti
, T.
Kampfrath
, and E.
Hendry
, “Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer
,” Appl. Phys. Lett.
114
(4
), 041107
(2019
).11.
E. T.
Papaioannou
, G.
Torosyan
, S.
Keller
, L.
Scheuer
, M.
Battiato
, V. K.
Mag-Usara
, J.
L'huillier
, M.
Tani
, and R.
Beigang
, “Efficient terahertz generation using Fe/Pt spintronic emitters pumped at different wavelengths
,” IEEE Trans. Magn.
54
(11
), 1
–5
(2018
).12.
R.
Beigang
, E. T.
Papaioannou
, L.
Scheuer
, S.
Keller
, G.
Torosyan
, M.
Rahm
, D.
Sokoluk
, M.
Talara
, Y.
Oda
, H.
Kitahara
, J.
Afalla
, V. K.
Mag-usara
, and M.
Tani
, “Efficient terahertz generation using Fe/Pt spintronic emitters pumped at different wavelengths
,” Proc. SPIE
10917
, 109170O
(2019
).13.
T. H.
Dang
, J.
Hawecker
, E.
Rongione
, G.
Baez Flores
, D. Q.
To
, J. C.
Rojas-Sanchez
, H.
Nong
, J.
Mangeney
, J.
Tignon
, F.
Godel
, S.
Collin
, P.
Seneor
, M.
Bibes
, A.
Fert
, M.
Anane
, J.-M.
George
, L.
Vila
, M.
Cosset-Cheneau
, D.
Dolfi
, R.
Lebrun
, P.
Bortolotti
, K.
Belashchenko
, S.
Dhillon
, and H.
Jaffrès
, “Ultrafast spin-currents and charge conversion at 3d-5d interfaces probed by time-domain terahertz spectroscopy
,” Appl. Phys. Rev.
7
(4
), 041409
(2020
).14.
W.-T.
Lu
, Y.
Zhao
, M.
Battiato
, Y.
Wu
, and Z.
Yuan
, “Interface reflectivity of a superdiffusive spin current in ultrafast demagnetization and terahertz emission
,” Phys. Rev. B
101
, 014435
(2020
).15.
J.
Hawecker
, T.-H.
Dang
, E.
Rongione
, J.
Boust
, S.
Collin
, J.-M.
George
, H.-J.
Drouhin
, Y.
Laplace
, R.
Grasset
, J.
Dong
, J.
Mangeney
, J.
Tignon
, H.
Jaffrès
, L.
Perfetti
, and S.
Dhillon
, “Spin injection efficiency at metallic interfaces probed by THz emission spectroscopy
,” Adv. Opt. Mater.
9
(17
), 2100412
(2021
).16.
M. A.
Wahada
, E.
Sasioglu
, W.
Hoppe
, X.
Zhou
, H.
Deniz
, R.
Rouzegar
, T.
Kampfrath
, I.
Mertig
, S. S. P.
Parkin
, and G.
Woltersdorf
, “Atomic scale control of spin current transmission at interfaces
,” arXiv:2108.01770 (2021
).17.
P.
Laczkowski
, J.-C.
Rojas-Sánchez
, W.
Savero-Torres
, H.
Jaffrès
, N.
Reyren
, C.
Deranlot
, L.
Notin
, C.
Beigné
, A.
Marty
, J.-P.
Attané
, L.
Vila
, J.-M.
George
, and A.
Fert
, “Experimental evidences of a large extrinsic spin Hall effect in AuW alloy
,” Appl. Phys. Lett.
104
(14
), 142403
(2014
).18.
P.
Laczkowski
, H.
Jaffrès
, W.
Savero-Torres
, J.-C.
Rojas-Sánchez
, Y.
Fu
, N.
Reyren
, C.
Deranlot
, L.
Notin
, C.
Beigné
, J.-P.
Attané
, L.
Vila
, J.-M.
George
, and A.
Marty
, “Evaluation of spin diffusion length of AuW alloys using spin absorption experiments in the limit of large spin-orbit interactions
,” Phys. Rev. B
92
, 214405
(2015
).19.
P.
Laczkowski
, Y.
Fu
, H.
Yang
, J.-C.
Rojas-Sánchez
, P.
Noel
, V. T.
Pham
, G.
Zahnd
, C.
Deranlot
, S.
Collin
, C.
Bouard
, P.
Warin
, V.
Maurel
, M.
Chshiev
, A.
Marty
, J.-P.
Attané
, A.
Fert
, H.
Jaffrès
, L.
Vila
, and J.-M.
George
, “Large enhancement of the spin Hall effect in Au by side-jump scattering on Ta impurities
,” Phys. Rev. B
96
, 140405
(2017
).20.
T. H.
Dang
, Q.
Barbedienne
, D. Q.
To
, E.
Rongione
, N.
Reyren
, F.
Godel
, S.
Collin
, J. M.
George
, and H.
Jaffrès
, “Anomalous Hall effect in multilayers mediated by interface scattering and nonlocal spin conductivity
,” Phys. Rev. B
102
, 144405
(2020
).21.
D.
Yang
, J.
Liang
, C.
Zhou
, L.
Sun
, R.
Zheng
, S.
Luo
, Y.
Wu
, and J.
Qi
, “Powerful and tunable THz emitters based on the Fe/Pt magnetic heterostructure
,” Adv. Opt. Mater.
4
(12
), 1944
–1949
(2016
).22.
Z.
Feng
, R.
Yu
, Y.
Zhou
, H.
Lu
, W.
Tan
, H.
Deng
, Q.
Liu
, Z.
Zhai
, L.
Zhu
, J.
Cai
, B.
Miao
, and H.
Ding
, “Highly Efficient spintronic terahertz emitter enabled by metal–dielectric photonic crystal
,” Adv. Opt. Mater.
6
(23
), 1800965
(2018
).23.
R.
Schneider
, M.
Fix
, J.
Bensmann
, S.
Michaelis de Vasconcellos
, M.
Albrecht
, and R.
Bratschitsch
, “Composition-dependent ultrafast THz emission of spintronic CoFe/Pt thin films
,” Appl. Phys. Lett.
120
(4
), 042404
(2022
).24.
M.
Meinert
, B.
Gliniors
, O.
Gueckstock
, T. S.
Seifert
, L.
Liensberger
, M.
Weiler
, S.
Wimmer
, H.
Ebert
, and T.
Kampfrath
, “High-throughput techniques for measuring the spin Hall effect
,” Phys. Rev. Appl.
14
, 064011
(2020
).25.
O.
Gueckstock
, L.
Nádvorník
, M.
Gradhand
, T. S.
Seifert
, G.
Bierhance
, R.
Rouzegar
, M.
Wolf
, M.
Vafaee
, J.
Cramer
, M. A.
Syskaki
, G.
Woltersdorf
, I.
Mertig
, G.
Jakob
, M.
Kläui
, and T.
Kampfrath
, “Terahertz spin-to-charge conversion by interfacial skew scattering in metallic bilayers
,” Adv. Mater.
33
(9
), 2006281
(2021
).26.
E.
Rongione
, S.
Fragkos
, L.
Baringthon
, J.
Hawecker
, E.
Xenogiannopoulou
, P.
Tsipas
, C.
Song
, M.
Mičica
, J.
Mangeney
, J.
Tignon
, T.
Boulier
, N.
Reyren
, R.
Lebrun
, J.-M.
George
, P.
Le Fèvre
, S.
Dhillon
, A.
Dimoulas
, and H.
Jaffrès
, “Ultrafast spin-charge conversion at SnBi2Te4/Co topological insulator interfaces probed by terahertz emission spectroscopy
,” Adv. Opt. Mater.
(published online 2021
).27.
28.
X.
Qiu
, W.
Legrand
, P.
He
, Y.
Wu
, J.
Yu
, R.
Ramaswamy
, A.
Manchon
, and H.
Yang
, “Enhanced spin-orbit torque via modulation of spin current absorption
,” Phys. Rev. Lett
117
, 217206
(2016
).29.
K.
Gupta
, R. J. H.
Wesselink
, R.
Liu
, Z.
Yuan
, and P. J.
Kelly
, “Disorder dependence of interface spin memory loss
,” Phys. Rev. Lett
124
, 087702
(2020
).30.
S.
Kaltenborn
, Y.-H.
Zhu
, and H. C.
Schneider
, “Wave-diffusion theory of spin transport in metals after ultrashort-pulse excitation
,” Phys. Rev. B
85
, 235101
(2012
).31.
D. M.
Nenno
, R.
Binder
, and H. C.
Schneider
, “Simulation of hot-carrier dynamics and terahertz emission in laser-excited metallic bilayers
,” Phys. Rev. Appl.
11
, 054083
(2019
).32.
J.-C.
Rojas-Sánchez
, N.
Reyren
, P.
Laczkowski
, W.
Savero
, J.-P.
Attané
, C.
Deranlot
, M.
Jamet
, J.-M.
George
, L.
Vila
, and H.
Jaffrès
, “Spin pumping and inverse spin Hall effect in platinum: The essential role of spin-memory loss at metallic interfaces
,” Phys. Rev. Lett
112
, 106602
(2014
).33.
E.
Sagasta
, Y.
Omori
, M.
Isasa
, M.
Gradhand
, L. E.
Hueso
, Y.
Niimi
, Y.
Otani
, and F.
Casanova
, “Tuning the spin Hall effect of Pt from the moderately dirty to the superclean regime
,” Phys. Rev. B
94
, 060412
(2016
).34.
A. J.
Berger
, E. R. J.
Edwards
, H. T.
Nembach
, O.
Karis
, M.
Weiler
, and T. J.
Silva
, “Determination of the spin Hall effect and the spin diffusion length of Pt from self-consistent fitting of damping enhancement and inverse spin-orbit torque measurements
,” Phys. Rev. B
98
, 024402
(2018
).35.
S.
Heidtfeld
, R.
Adam
, T.
Kubota
, K.
Takanashi
, D.
Cao
, C.
Schmitz-Antoniak
, D. E.
Bürgler
, F.
Wang
, C.
Greb
, G.
Chen
, I.
Komissarov
, H.
Hardtdegen
, M.
Mikulics
, R.
Sobolewski
, S.
Suga
, and C. M.
Schneider
, “Generation of terahertz transients from Co2Fe0.4Mn0.6Si-Heusler-alloy/normal-metal nanobilayers excited by femtosecond optical pulses
,” Phys. Rev. Res.
3
, 043025
(2021
).36.
R.
Gupta
, S.
Husain
, A.
Kumar
, R.
Brucas
, A.
Rydberg
, and P.
Svedlindh
, “Co2FeAl full Heusler compound based spintronic terahertz emitter
,” Adv. Opt. Mater.
9
(10
), 2001987
(2021
).37.
G.
Bierhance
, A.
Markou
, O.
Gueckstock
, R.
Rouzegar
, Y.
Behovits
, A.
Chekhov
, M.
Wolf
, T. S.
Seifert
, C.
Felser
, and T.
Kampfrath
, “Spin-voltage-driven efficient terahertz spin currents from the magnetic Weyl semimetals Co2MnGa and Co2MnAl
,” arXiv:2111.15599 (2021
).38.
B. S.
Varaprasad
, A.
Rajanikanth
, Y. K.
Takahashi
, and K.
Hono
, “Enhanced spin polarization of Co2MnGe Heusler alloy by substitution of Ga for Ge
,” Applied Physics Express
3
, 023002
(2010
).39.
C.
Guillemard
, S.
Petit-Watelot
, L.
Pasquier
, D.
Pierre
, J.
Ghanbaja
, J.-C.
Rojas-Sánchez
, A.
Bataille
, J.
Rault
, P.
Le Fèvre
, F.
Bertran
, and S.
Andrieu
, “Ultralow magnetic damping in -based Heusler compounds: Promising materials for spintronics
,” Phys. Rev. Appl.
11
, 064009
(2019
).40.
C.
Guillemard
, S.
Petit-Watelot
, J.-C.
Rojas-Sánchez
, J.
Hohlfeld
, J.
Ghanbaja
, A.
Bataille
, L.
Fèvre
, F.
Bertran
, and S.
Andrieu
, “Polycrystalline Co2Mn-based Heusler thin films with high spin polarization and low magnetic damping
,” Appl. Phys. Lett.
115
(17
), 172401
(2019
).41.
H.
Chudo
, K.
Ando
, K.
Saito
, S.
Okayasu
, R.
Haruki
, Y.
Sakuraba
, H.
Yasuoka
, K.
Takanashi
, and E.
Saitoh
, “Spin pumping efficiency from half metallic Co2MnSi
,” J. Appl. Phys.
109
(7
), 073915
(2011
).42.
Y.
Sasaki
, S.
Sugimoto
, Y. K.
Takahashi
, and S.
Kasai
, “Spin injection efficiency through the pumping in epitaxial Co2MnSi/Pt thin film
,” AIP Adv.
10
(8
), 085311
(2020
).43.
L.
Leiva
, S.
Granville
, Y.
Zhang
, S.
Dushenko
, E.
Shigematsu
, T.
Shinjo
, R.
Ohshima
, Y.
Ando
, and M.
Shiraishi
, “Giant spin Hall angle in the Heusler alloy Weyl ferromagnet
,” Phys. Rev. B
103
, L041114
(2021
).44.
Q.
Zhang
, Z.
Luo
, H.
Li
, Y.
Yang
, X.
Zhang
, and Y.
Wu
, “Terahertz emission from anomalous Hall effect in a single-layer ferromagnet
,” Phys. Rev. Appl.
12
, 054027
(2019
).45.
A.
Markou
, D.
Kriegner
, J.
Gayles
, L.
Zhang
, Y.-C.
Chen
, B.
Ernst
, Y.-H.
Lai
, W.
Schnelle
, Y.-H.
Chu
, Y.
Sun
, and C.
Felser
, “Thickness dependence of the anomalous Hall effect in thin films of the topological semimetal
,” Phys. Rev. B
100
, 054422
(2019
).46.
L.
Nádvorník
, M.
Borchert
, L.
Brandt
, R.
Schlitz
, K. A.
de Mare
, K.
Výborný
, I.
Mertig
, G.
Jakob
, M.
Kläui
, S. T. B.
Goennenwein
, M.
Wolf
, G.
Woltersdorf
, and T.
Kampfrath
, “Broadband terahertz probes of anisotropic magnetoresistance disentangle extrinsic and intrinsic contributions
,” Phys. Rev. X
11
, 021030
(2021
).47.
H.
Jaffrès
, J.-M.
George
, and A.
Fert
, “Spin transport in multiterminal devices: Large spin signals in devices with confined geometry
,” Phys. Rev. B
82
, 140408
(2010
).48.
P.
Laczkowski
, L.
Vila
, V.-D.
Nguyen
, A.
Marty
, J.-P.
Attané
, H.
Jaffrès
, J.-M.
George
, and A.
Fert
, “Enhancement of the spin signal in permalloy/gold multiterminal nanodevices by lateral confinement
,” Phys. Rev. B
85
, 220404
(2012
).49.
P.
Jiménez-Cavero
, O.
Gueckstock
, L.
Nádvorník
, I.
Lucas
, T. S.
Seifert
, M.
Wolf
, R.
Rouzegar
, P. W.
Brouwer
, S.
Becker
, G.
Jakob
, M.
Kläui
, C.
Guo
, C.
Wan
, X.
Han
, Z.
Jin
, H.
Zhao
, D.
Wu
, L.
Morellón
, and T.
Kampfrath
, “Tuning laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport
,” arXiv:2110.05462v2 (2021
).50.
H.
Reichlova
, R.
Schlitz
, S.
Beckert
, P.
Swekis
, A.
Markou
, Y.-C.
Chen
, D.
Kriegner
, S.
Fabretti
, G.
Hyeon Park
, A.
Niemann
, S.
Sudheendra
, A.
Thomas
, K.
Nielsch
, C.
Felser
, and S. T. B.
Goennenwein
, “Large anomalous Nernst effect in thin films of the Weyl semimetal Co2MnGa
,” Appl. Phys. Lett.
113
(21
), 212405
(2018
).© 2022 Author(s). Published under an exclusive license by AIP Publishing.
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