Future generations of magnetic random access memory demand magnetic tunnel junctions that can provide simultaneously high magnetoresistance, strong retention, low switching energy, and small cell size below 10 nm. Here, we study perpendicular magnetic tunnel junctions with composite free layers, where multiple ferromagnet/nonmagnet interfaces can contribute to the thermal stability. Different nonmagnetic materials (MgO, Ta, and Mo) have been employed as the coupling layers in these multi-interface free layers. The evolution of junction properties under different annealing conditions is investigated. A strong dependence of the tunneling magnetoresistance on the thickness of the first CoFeB layer has been observed. In junctions where Mo and MgO are used as coupling layers, a large tunneling magnetoresistance above 200% has been achieved after 400 °C annealing.
References
1.
S.
Yuasa
, K.
Hono
, G.
Hu
, and D. C.
Worledge
, “Materials for spin-transfer-torque magnetoresistive random-access memory
,” MRS Bull.
43
, 352
–357
(2018
).2.
D.
Apalkov
, B.
Dieny
, and J. M.
Slaughter
, “Magnetoresistive random access memory
,” Proc. IEEE
104
, 1796
–1830
(2016
).3.
D. C.
Ralph
and M. D.
Stiles
, “Spin transfer torques
,” J. Magn. Magn. Mater.
320
, 1190
–1216
(2008
).4.
A.
Brataas
, A. D.
Kent
, and H.
Ohno
, “Current-induced torques in magnetic materials
,” Nat. Mater.
11
, 372
–381
(2012
).5.
A.
Manchon
, J.
Železný
, I. M.
Miron
, T.
Jungwirth
, J.
Sinova
, A.
Thiaville
, K.
Garello
, and P.
Gambardella
, “Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems
,” Rev. Mod. Phys.
91
, 035004
(2019
).6.
F.
Matsukura
, Y.
Tokura
, and H.
Ohno
, “Control of magnetism by electric fields
,” Nat. Nanotechnol.
10
, 209
–220
(2015
).7.
W.-G.
Wang
, M.
Li
, S.
Hageman
, and C. L.
Chien
, “Electric-field-assisted switching in magnetic tunnel junctions
,” Nat. Mater.
11
, 64
–68
(2012
).8.
T.
Newhouse-Illige
, Y.
Liu
, M.
Xu
, D.
Reifsnyder Hickey
, A.
Kundu
, H.
Almasi
, C.
Bi
, X.
Wang
, J. W.
Freeland
, D. J.
Keavney
, C. J.
Sun
, Y. H.
Xu
, M.
Rosales
, X. M.
Cheng
, S.
Zhang
, K. A.
Mkhoyan
, W. G.
Wang
, D. R.
Hickey
, A.
Kundu
, H.
Almasi
, C.
Bi
, X.
Wang
, J. W.
Freeland
, D. J.
Keavney
, C. J.
Sun
, Y. H.
Xu
, M.
Rosales
, X. M.
Cheng
, S.
Zhang
, K. A.
Mkhoyan
, and W. G.
Wang
, “Voltage-controlled interlayer coupling in perpendicularly magnetized magnetic tunnel junctions
,” Nat. Commun.
8
, 15232
(2017
).9.
X.
He
, Y.
Wang
, N.
Wu
, A. N.
Caruso
, E.
Vescovo
, K. D.
Belashchenko
, P. A.
Dowben
, and C.
Binek
, “Robust isothermal electric control of exchange bias at room temperature
,” Nat. Mater.
9
, 579
–585
(2010
).10.
C.
Bi
, C.
Sun
, M.
Xu
, T.
Newhouse-Illige
, P. M.
Voyles
, and W.
Wang
, “Electrical control of metallic heavy-metal-ferromagnet interfacial states
,” Phys. Rev. Appl.
8
, 034003
(2017
).11.
B.
Dieny
and M.
Chshiev
, “Perpendicular magnetic anisotropy at transition metal/oxide interfaces and applications
,” Rev. Mod. Phys.
89
, 025008
(2017
).12.
H.
Almasi
, D. R.
Hickey
, T.
Newhouse-Illige
, M.
Xu
, M. R.
Rosales
, S.
Nahar
, J. T.
Held
, K. A.
Mkhoyan
, and W. G.
Wang
, “Enhanced tunneling magnetoresistance and perpendicular magnetic anisotropy in Mo/CoFeB/MgO magnetic tunnel junctions
,” Appl. Phys. Lett.
106
, 182406
(2015
).13.
H.
Almasi
, C. L.
Sun
, X.
Li
, T.
Newhouse-Illige
, C.
Bi
, K. C.
Price
, S.
Nahar
, C.
Grezes
, Q.
Hu
, P.
Khalili Amiri
, K. L.
Wang
, P. M.
Voyles
, and W. G.
Wang
, “Perpendicular magnetic tunnel junction with W seed and capping layers
,” J. Appl. Phys.
121
, 153902
(2017
).14.
H.
Almasi
, M.
Xu
, Y.
Xu
, T.
Newhouse-Illige
, and W. G.
Wang
, “Effect of Mo insertion layers on the magnetoresistance and perpendicular magnetic anisotropy in Ta/CoFeB/MgO junctions
,” Appl. Phys. Lett.
109
, 032401
(2016
).15.
D. L.
Zhang
, C.
Sun
, Y.
Lv
, K. B.
Schliep
, Z.
Zhao
, J. Y.
Chen
, P. M.
Voyles
, and J. P.
Wang
, “L10 Fe-Pd synthetic antiferromagnet through an fcc Ru spacer utilized for perpendicular magnetic tunnel junctions
,” Phys. Rev. Appl.
9
, 044028
(2018
).16.
D. L.
Zhang
, K. B.
Schliep
, R. J.
Wu
, P.
Quarterman
, D.
Reifsnyder Hickey
, Y.
Lv
, X.
Chao
, H.
Li
, J. Y.
Chen
, Z.
Zhao
, M.
Jamali
, K. A.
Mkhoyan
, and J. P.
Wang
, “Enhancement of tunneling magnetoresistance by inserting a diffusion barrier in L10-FePd perpendicular magnetic tunnel junctions
,” Appl. Phys. Lett.
112
, 152401
(2018
).17.
T.
Kubota
, Q. L.
Ma
, S.
Mizukami
, X. M.
Zhang
, H.
Naganuma
, M.
Oogane
, Y.
Ando
, and T.
Miyazaki
, “Magnetic tunnel junctions of perpendicularly magnetized L10-MnGa/Fe/MgO/CoFe structures: Fe-layer-thickness dependences of magnetoresistance effect and tunnelling conductance spectra
,” J. Phys. D. Appl. Phys.
46
, 155001
(2013
).18.
W. H.
Butler
, X.-G.
Zhang
, T. C.
Schulthess
, and J. M.
MacLaren
, “Spin-dependent tunneling conductance of Fe/MgO/Fe sandwiches
,” Phys. Rev. B
63
, 054416
(2001
).19.
K.
Watanabe
, B.
Jinnai
, S.
Fukami
, H.
Sato
, and H.
Ohno
, “Shape anisotropy revisited in single-digit nanometer magnetic tunnel junctions
,” Nat. Commun.
9
, 663
(2018
).20.
B.
Jinnai
, J.
Igarashi
, K.
Watanabe
, T.
Funatsu
, H.
Sato
, S.
Fukami
, and H.
Ohno
, “High-performance shape-anisotropy magnetic tunnel junctions down to 2.3 nm
,” in 2020 IEEE International Electron Devices Meeting (IEDM)
(IEEE
, 2020
), pp. 24.6.1
–24.6.4
.21.
H.
Sato
, M.
Yamanouchi
, S.
Ikeda
, S.
Fukami
, F.
Matsukura
, and H.
Ohno
, “Perpendicular-anisotropy CoFeB-MgO magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure
,” Appl. Phys. Lett.
101
, 022414
(2012
).22.
H.
Sato
, E. C. I.
Enobio
, M.
Yamanouchi
, S.
Ikeda
, S.
Fukami
, S.
Kanai
, F.
Matsukura
, and H.
Ohno
, “Properties of magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure down to junction diameter of 11 nm
,” Appl. Phys. Lett.
105
, 062403
(2014
).23.
S.-E.
Lee
, J.-U.
Baek
, and J.-G.
Park
, “Highly enhanced TMR ratio and Δ for double MgO-based p-MTJ spin-valves with top Co2Fe6B2 free layer by nanoscale-thick iron diffusion-barrier
,” Sci. Rep.
7
, 11907
(2017
).24.
J. H.
Kim
, J. B.
Lee
, G. G.
An
, S. M.
Yang
, W. S.
Chung
, H. S.
Park
, and J. P.
Hong
, “Ultrathin W space layer-enabled thermal stability enhancement in a perpendicular MgO/CoFeB/W/CoFeB/MgO recording frame
,” Sci. Rep.
5
, 16903
(2015
).25.
J.
Chatterjee
, A.
Chavent
, F.
Fettar
, S.
Auffret
, C.
Ducruet
, I.
Joumard
, L.
Vila
, R. C.
Sousa
, L.
Prejbeanu
, and B.
Dieny
, “Reduced thermal variation of perpendicular magnetic anisotropy in magnetically stiffened dual-W composite storage layer for spin-transfer-torque magnetic random-access memory
,” Phys. Rev. Appl.
12
, 044043
(2019
).26.
K.
Nishioka
, H.
Honjo
, H.
Naganuma
, T. V. A.
Nguyen
, M.
Yasuhira
, S.
Ikeda
, and T.
Endoh
, “Enhancement of magnetic coupling and magnetic anisotropy in MTJs with multiple CoFeB/MgO interfaces for high thermal stability Enhancement of magnetic coupling and magnetic anisotropy in MTJs with multiple CoFeB/MgO interfaces for high thermal stability
,” AIP Adv.
11
, 025231
(2021
).27.
K.
Nishioka
, H.
Sato
, T.
Endoh
, H.
Honjo
, S.
Ikeda
, T.
Watanabe
, S.
Miura
, H.
Inoue
, T.
Tanigawa
, Y.
Noguchi
, and M.
Yasuhira
, “Novel quad-interface MTJ technology and its first demonstration with high thermal stability factor and switching efficiency for STT-MRAM beyond 2X nm
,” IEEE Trans. Electron Devices
67
, 995
–1000
(2020
).28.
T.
Newhouse-Illige
, Y. H.
Xu
, Y. H.
Liu
, S.
Huang
, H.
Kato
, C.
Bi
, M.
Xu
, B.
Leroy
, and W. G.
Wang
, “Temperature dependence of interlayer coupling in perpendicular magnetic tunnel junctions with GdOx barriers
,” Appl. Phys. Lett.
112
, 072404
(2018
).29.
M.
Xu
, M.
Li
, P.
Khanal
, A.
Habiboglu
, B.
Insana
, Y.
Xiong
, T.
Peterson
, J. C.
Myers
, D.
Ortega
, H.
Qu
, C. L.
Chien
, W.
Zhang
, J. P.
Wang
, and W. G.
Wang
, “Voltage-controlled antiferromagnetism in magnetic tunnel junctions
,” Phys. Rev. Lett.
124
, 187701
(2020
).30.
H. X.
Yang
, M.
Chshiev
, B.
Dieny
, J. H.
Lee
, A.
Manchon
, and K. H.
Shin
, “First-principles investigation of the very large perpendicular magnetic anisotropy at Fe|MgO and Co|MgO interfaces
,” Phys. Rev. B
84
, 054401
(2011
).31.
P.
Bruno
, “Tight-binding approach to the orbital magnetic moment and magnetocrystalline anisotropy of transition-metal monolayers
,” Phys. Rev. B
39
, 865
(1989
).32.
D.
Weller
, J.
Stohr
, R.
Nakajima
, A.
Carl
, M. G.
Samant
, C.
Chappert
, P.
Beauvillain
, P.
Veillet
, and G. A.
Held
, “Microscopic origin of magnetic anisotropy in Au/Co/Au probed with X-Ray magnetic circular dichroism
,” Phys. Rev. Lett.
75
, 3752
–3755
(1995
).33.
K. Y.
Camsari
, A. Z.
Pervaiz
, R.
Faria
, E. E.
Marinero
, and S.
Datta
, “Ultrafast spin-transfer-torque switching of synthetic ferrimagnets
,” IEEE Magn. Lett.
7
, 1
–5
(2016
).34.
S.
Mangin
, D.
Ravelosona
, J. A.
Katine
, M. J.
Carey
, B. D.
Terris
, and E. E.
Fullerton
, “Current-induced magnetization reversal in nanopillars with perpendicular anisotropy
,” Nat. Mater.
5
, 210
–215
(2006
).35.
E.
Liu
, J.
Swerts
, S.
Couet
, S.
Mertens
, Y.
Tomczak
, T.
Lin
, V.
Spampinato
, A.
Franquet
, S.
Van Elshocht
, G.
Kar
, A.
Furnemont
, and J.
De Boeck
, “[Co/Ni]-CoFeB hybrid free layer stack materials for high density magnetic random access memory applications
,” Appl. Phys. Lett.
108
, 132405
(2016
).36.
S.
Ikeda
, K.
Miura
, H.
Yamamoto
, K.
Mizunuma
, H. D.
Gan
, M.
Endo
, S.
Kanai
, J.
Hayakawa
, F.
Matsukura
, and H.
Ohno
, “A perpendicular-anisotropy CoFeB-MgO magnetic tunnel junction
,” Nat. Mater.
9
, 721
–724
(2010
).37.
D. C.
Worledge
, G.
Hu
, D. W.
Abraham
, J. Z.
Sun
, P. L.
Trouilloud
, J.
Nowak
, S.
Brown
, M. C.
Gaidis
, E. J.
O'Sullivan
, and R. P.
Robertazzi
, “Spin torque switching of perpendicular Ta|CoFeB|MgO-based magnetic tunnel junctions
,” Appl. Phys. Lett.
98
, 022501
(2011
).38.
J.
Faure-Vincent
, C.
Tiusan
, C.
Bellouard
, E.
Popova
, M.
Hehn
, F.
Montaigne
, and A.
Schuhl
, “Interlayer magnetic coupling interactions of two ferromagnetic layers by spin polarized tunneling
,” Phys. Rev. Lett.
89
, 107206
(2002
).39.
T.
Katayama
, S.
Yuasa
, J.
Velev
, M. Y.
Zhuravlev
, S. S.
Jaswal
, and E. Y.
Tsymbal
, “Interlayer exchange coupling in Fe/MgO/Fe magnetic tunnel junctions
,” Appl. Phys. Lett.
89
, 112503
(2006
).40.
L. E.
Nistor
, B.
Rodmacq
, S.
Auffret
, A.
Schuhl
, M.
Chshiev
, and B.
Dieny
, “Oscillatory interlayer exchange coupling in MgO tunnel junctions with perpendicular magnetic anisotropy
,” Phys. Rev. B
81
, 220407(R)
(2010
).41.
W. G.
Wang
, C.
Ni
, G. X.
Miao
, C.
Weiland
, L. R.
Shah
, X.
Fan
, P.
Parson
, J.
Jordan-Sweet
, X. M.
Kou
, Y. P.
Zhang
, R.
Stearrett
, E. R.
Nowak
, R.
Opila
, J. S.
Moodera
, and J. Q.
Xiao
, “Understanding tunneling magnetoresistance during thermal annealing in MgO-based junctions with CoFeB electrodes
,” Phys. Rev. B
81
, 144406
(2010
).42.
W. G.
Wang
, J.
Jordan-Sweet
, G. X.
Miao
, C.
Ni
, A.
Rumaiz
, L.
Shah
, X.
Fan
, P.
Parson
, R.
Stearrett
, R.
Nowak
, J. S.
Moodera
, and J. Q.
Xiao
, “In situ characterization of rapid crystallization of amorphous CoFeB electrodes in CoFeB/MgO/CoFeB junctions during thermal annealing
,” Appl. Phys. Lett.
95
, 242501
(2009
).43.
W.-G.
Wang
, S.
Hageman
, M.
Li
, S.
Huang
, X.
Kou
, X.
Fan
, J. Q.
Xiao
, and C. L.
Chien
, “Rapid thermal annealing study of magnetoresistance and perpendicular anisotropy in magnetic tunnel junctions based on MgO and CoFeB
,” Appl. Phys. Lett.
99
, 102502
(2011
).44.
S. S. P.
Parkin
, “Systematic variation of the strength and oscillation period of indirect magnetic exchange coupling through the 3d, 4d, and 5d transition metals
,” Phys. Rev. Lett.
67
, 3598
–3601
(1991
).45.
C. W.
Cheng
, T. I.
Cheng
, C. H.
Shiue
, C. L.
Weng
, Y. C.
Tsai
, and G.
Chern
, “Synthetic antiferromagnetic MgO/CoFeB/Ta(x)/CoFeB/MgO structures with perpendicular magnetic anisotropy
,” IEEE Trans. Magn.
49
, 4433
–4436
(2013
).46.
P.
Bruno
, “Theory of interlayer magnetic coupling
,” Phys. Rev. B
52
, 411
(1995
).47.
T.
Liu
, Y.
Zhang
, J. W.
Cai
, and H. Y.
Pan
, “Thermally robust Mo/CoFeB/MgO trilayers with strong perpendicular magnetic anisotropy
,” Sci. Rep.
4
, 5895
(2014
).48.
S.
Husain
, A.
Kumar
, V.
Barwal
, N.
Behera
, S.
Akansel
, P.
Svedlindh
, and S.
Chaudhary
, “Spin pumping in ion-beam sputtered C o2FeAl/Mo bilayers: Interfacial Gilbert damping
,” Phys. Rev. B
97
, 064420
(2018
).49.
X.
Zhang
, Y.
Zhang
, and J. W.
Cai
, “Antiferromagnetically coupled perpendicular magnetic anisotropic CoFeB/MgO films across a Mo spacer with high thermal stability
,” J. Appl. Phys
118
, 143903
(2015
).© 2021 Author(s). Published under an exclusive license by AIP Publishing.
2021
Author(s)
You do not currently have access to this content.
