Field-free switching through bulk spin−orbit torque inL1₀-FePt films deposited on vicinal substrates

Abstract

L1₀-FePt distinguishes itself for its ultrahigh perpendicular magnetic anisotropy (PMA), enabling thermally stabile memory cells to scale down to 3 nm. The recently discovered “bulk” spin−orbit torques inL1₀-FePt provide an efficient and scalable way to manipulate the L1₀-FePt magnetization. However, the existence of an external field during the switching limits its practical application, and therefore field-free switching of L1₀-FePt is highly demanded. In this manuscript, by growing the L1₀-FePt film on vicinal MgO (001) substrates, we realize the field-free switching of L1₀-FePt. This method is different from previously established strategies as it does not need to add other functional layers or create asymmetry in the film structure. The dependence on the vicinal angle, film thickness, and growth temperature demonstrates a wide operation window for the field-free switching of L1₀-FePt. We confirm the physical origin of the field-free switching is due to the tilted anisotropy of L1₀-FePt induced by the vicinal surface. We also quantitatively characterize the spin-orbit torques in the L1₀-FePt films. Our results extend beyond the established strategies to realize field-free switching, and potentially could be applied to mass production.

Graphical abstract

Keywords

spin−orbit torque / vicinal substrates / field-free switching

References

[1] S.Sun, C.B. Murray, D.Weller, L.Folks, A.Moser. Monodisperse FePt nanoparticles and ferromagnetic FePt nanocrystal superlattices. Science , 2000, 287( 5460): 1989

[2] M.Tang, K.Shen, S.Xu, H.Yang, S.Hu, W.Lü, C.Li, M.Li, Z.Yuan, S.J. Pennycook, K.Xia, A.Manchon, S.Zhou, X.Qiu. Bulk spin torque-driven perpendicular magnetization switching in L1₀ FePt single layer. Adv. Mater. , 2020, 32( 31): 2002607

[3] L.Liu, J.Yu, R.Gonzalez-Hernandez, C.Li, J.Deng, W.Lin, C.Zhou, T.Zhou, J.Zhou, H.Wang, R.Guo, H.Y. Yoong, G.M. Chow, X.Han, B.Dupé, J.Železný, J.Sinova, J.Chen. Electrical switching of perpendicular magnetization in a single ferromagnetic layer. Phys. Rev. B , 2020, 101( 22): 220402

[4] L.Zhu, D.C. Ralph, R.A. Buhrman. Unveiling the mechanism of bulk spin−orbit torques within chemically disordered Fe_xPt_1−x single layers. Adv. Funct. Mater. , 2021, 31( 36): 2103898

[5] S.Q. Zheng, K.K. Meng, Q.B. Liu, J.K. Chen, J.Miao, X.G. Xu, Y.Jiang. Disorder dependent spin-orbit torques in L1₀ FePt single layer. Appl. Phys. Lett. , 2020, 117( 24): 242403

[6] I.Mihai Miron, G.Gaudin, S.Auffret, B.Rodmacq, A.Schuhl, S.Pizzini, J.Vogel, P.Gambardella. Current-driven spin torque induced by the Rashba effect in a ferromagnetic metal layer. Nat. Mater. , 2010, 9( 3): 230

[7] L.Liu, O.J. Lee, T.J. Gudmundsen, D.C. Ralph, R.A. Buhrman. Current-induced switching of perpendicularly magnetized magnetic layers using spin torque from the spin Hall effect. Phys. Rev. Lett. , 2012, 109( 9): 096602

[8] L.Liu, C.F. Pai, Y.Li, H.W. Tseng, D.C. Ralph, R.A. Buhrman. Spin-torque switching with the giant spin Hall effect of tantalum. Science , 2012, 336( 6081): 555

[9] Q.Shao, P.Li, L.Liu, H.Yang, S.Fukami, A.Razavi, H.Wu, K.Wang, F.Freimuth, Y.Mokrousov, M.D. Stiles, S.Emori, A.Hoffmann, J.Akerman, K.Roy, J.P. Wang, S.H. Yang, K.Garello, W.Zhang. Roadmap of spin−orbit torques. IEEE Trans. Magn. , 2021, 57( 7): 1

[10] W.Kong, C.Wan, X.Wang, B.Tao, L.Huang, C.Fang, C.Guo, Y.Guang, M.Irfan, X.Han. Spin-orbit torque switching in a T-type magnetic configuration with current orthogonal to easy axes. Nat. Commun. , 2019, 10( 1): 233

[11] S.Fukami, C.Zhang, S.DuttaGupta, A.Kurenkov, H.Ohno. Magnetization switching by spin−orbit torque in an antiferromagnet−ferromagnet bilayer system. Nat. Mater. , 2016, 15( 5): 535

[12] K.Eason, S.G. Tan, M.B. A. Jalil, J.Y. Khoo. Bistable perpendicular switching with in-plane spin polarization and without external fields. Phys. Lett. A , 2013, 377( 37): 2403

[13] L.You, O.Lee, D.Bhowmik, D.Labanowski, J.Hong, J.Bokor, S.Salahuddin. Switching of perpendicularly polarized nanomagnets with spin−orbit torque without an external magnetic field by engineering a tilted anisotropy. Proc. Natl. Acad. Sci. USA , 2015, 112( 33): 10310

[14] L.Liu, Q.Qin, W.Lin, C.Li, Q.Xie, S.He, X.Shu, C.Zhou, Z.Lim, J.Yu, W.Lu, M.Li, X.Yan, S.J. Pennycook, J.Chen. Current-induced magnetization switching in all-oxide heterostructures. Nat. Nanotechnol. , 2019, 14( 10): 939

[15] F.Leroy, P.Mueller, J.J. Metois, O.Pierre-Louis. Vicinal silicon surfaces: From step density wave to faceting. Phys. Rev. B , 2007, 76( 4): 045402

[16] C.Tegenkamp. Vicinal surfaces for functional nanostructures. J. Phys.: Condens. Matter , 2009, 21( 1): 013002

[17] S.Ma, A.Tan, J.X. Deng, J.Li, Z.D. Zhang, C.Hwang, Z.Q. Qiu. Tailoring the magnetic anisotropy of Py/Ni bilayer films using well aligned atomic steps on Cu(001). Sci. Rep. , 2015, 5( 1): 1

[18] R.K. Kawakami, E.J. Escorcia-Aparicio, Z.Q. Qiu. Symmetry-induced magnetic anisotropy in Fe films grown on stepped Ag(001). Phys. Rev. Lett. , 1996, 77( 12): 2570

[19] S.Dhesi, H.Dürr, G.Van der Laan. Canted spin structures in Ni films on stepped Cu(001). Phys. Rev. B , 1999, 59( 13): 8408

[20] J.Choi, J.Wu, Y.Z. Wu, C.Won, A.Scholl, A.Doran, T.Owens, Z.Q. Qiu. Effect of atomic steps on the interfacial interaction of FeMn/Co films grown on vicinal Cu(001). Phys. Rev. B , 2007, 76( 5): 054407

[21] J.Zhu, Q.Li, J.X. Li, Z.Ding, J.H. Liang, X.Xiao, Y.M. Luo, C.Y. Hua, H.J. Lin, T.W. Pi, Z.Hu, C.Won, Y.Z. Wu. Antiferromagnetic spin reorientation transition in epitaxial NiO/CoO/MgO(001) systems. Phys. Rev. B , 2014, 90( 5): 054403

[22] P.He, L.Ma, Z.Shi, G.Guo, J.G. Zheng, Y.Xin, S.Zhou. Chemical composition tuning of the anomalous Hall effect in isoelectronic L1₀ FePd_1−xPt_x alloy films. Phys. Rev. Lett. , 2012, 109( 6): 066402

[23] S.Okamoto, N.Kikuchi, O.Kitakami, T.Miyazaki, Y.Shimada, K.Fukamichi. Chemical-order-dependent magnetic anisotropy and exchange stiffness constant of FePt (001) epitaxial films. Phys. Rev. B , 2002, 66( 2): 024413

[24] Z.Zhao, A.K. Smith, M.Jamali, J.P. Wang. External-field-free spin Hall switching of perpendicular magnetic nanopillar with a dipole-coupled composite structure. Adv. Electron. Mater. , 2020, 6( 5): 1901368

[25] A.van den Brink, G.Vermijs, A.Solignac, J.Koo, J.T. Kohlhepp, H.J. M. Swagten, B.Koopmans. Fieldfree magnetization reversal by spin-Hall effect and exchange bias. Nat. Commun. , 2016, 7( 1): 1

[26] M.Hayashi, J.Kim, M.Yamanouchi, H.Ohno. Quantitative characterization of the spin-orbit torque using harmonic Hall voltage measurements. Phys. Rev. B , 2014, 89( 14): 144425

[27] K.Garello, I.M. Miron, C.O. Avci, F.Freimuth, Y.Mokrousov, S.Blügel, S.Auffret, O.Boulle, G.Gaudin, P.Gambardella. Symmetry and magnitude of spin-orbit torques in ferromagnetic heterostructures. Nat. Nanotechnol. , 2013, 8( 8): 587

[28] C.O. Avci, A.Quindeau, C.F. Pai, M.Mann, L.Caretta, A.S. Tang, M.C. Onbasli, C.A. Ross, G.S. Beach. Current-induced switching in a magnetic insulator. Nat. Mater. , 2017, 16( 3): 309

[29] L.Zhu, D.C. Ralph, R.A. Buhrman. Maximizing spinorbit torque generated by the spin Hall effect of Pt. Appl. Phys. Rev. , 2021, 8( 3): 031308

[30] M.Filianina, J.P. Hanke, K.Lee, D.S. Han, S.Jaiswal, A.Rajan, G.Jakob, Y.Mokrousov, M.Kläui. Electric-field control of spin-orbit torques in perpendicularly magnetized W/CoFeB/MgO films. Phys. Rev. Lett. , 2020, 124( 21): 217701

[31] X.G. Ye, P.F. Zhu, W.Z. Xu, N.Shang, K.Liu, Z.M. Liao. Orbit-transfer torque driven field-free switching of perpendicular magnetization. Chin. Phys. Lett. , 2022, 39( 3): 037303

[32] D.Lee, D.Go, H.J. Park, W.Jeong, H.W. Ko, D.Yun, D.Jo, S.Lee, G.Go, J.H. Oh, K.J. Kim, B.G. Park, B.C. Min, H.C. Koo, H.W. Lee, O.J. Lee, K.J. Lee. Orbital torque in magnetic bilayers. Nat. Commun. , 2021, 12( 1): 6710

[33] P.Perna, C.Rodrigo, E.Jiménez, N.Mikuszeit, F.J. Teran, L.Méchin, J.Camarero, R.Miranda. Magnetization reversal in half metallic La_0.7Sr_0.3MnO₃ films grown onto vicinal surfaces. J. Appl. Phys. , 2011, 109 : 07B107

[34] Y.Tao, C.Sun, W.Li, L.Yang, F.Jin, Y.Hui, H.Li, X.Wang, K.Dong. Field-free spin–orbit torque switching in L1₀-FePt single layer with tilted anisotropy. Appl. Phys. Lett. , 2022, 120( 10): 102405

Electronic supplementary material

The supplementary material is available in the online version of this article at https://doi.org/10.1007/s11467-022-1197-7 and https://journal.hep.com.cn/fop/EN/pdf/10.1007/s11467-022-1197-7 and is accessible for authorized users.

Acknowledgements

We thank Drs. Xuefeng Zhang, Jian Zhang, Lianze Ji, Shuai Huang for their help of lithography, XRD characterization and helpful discussion. This work was supported by the “Pioneer” and “Leading Goose” RD Program of Zhejiang Province (Grant No. 2022C01053), the National Natural Science Foundation of China (Grant No. 12274108, 11874135 and 12104119), the Key Research and Development Program of Zhejiang Province (Grant No. 2021C01039), and the Natural Science Foundation of Zhejiang Province, China (Grant Nos. LQ20F040005 and LQ21A050001).

RIGHTS & PERMISSIONS

2022 Higher Education Press