Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers

Subjects

Abstract

Magnetoresistive effects are usually invariant on inversion of the magnetization direction. In non-centrosymmetric conductors, however, nonlinear resistive terms can give rise to a current dependence that is quadratic in the applied voltage and linear in the magnetization. Here we demonstrate that such conditions are realized in simple bilayer metal films where the spin–orbit interaction and spin-dependent scattering couple the current-induced spin accumulation to the electrical conductivity. We show that the longitudinal resistance of Ta|Co and Pt|Co bilayers changes when reversing the polarity of the current or the sign of the magnetization. This unidirectional magnetoresistance scales linearly with current density and has opposite sign in Ta and Pt, which we associate with the modification of the interface scattering potential induced by the spin Hall effect in these materials. Our results suggest a route to control the resistance and detect magnetization switching in spintronic devices using a two-terminal geometry, which applies also to heterostructures including topological insulators.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Illustration of the unidirectional spin Hall magnetoresistance effect and sample layout.
Figure 2: Linear and nonlinear magnetoresistance.
Figure 3: Field and current dependence of the nonlinear magnetoresistance.
Figure 4: USMR as a function of NM thickness.
Figure 5: Modulation of the spin accumulation, spin-dependent electrochemical potential, and interface resistance by the SHE.

References

  1. 1

    Thomson, W. On the electro-dynamic qualities of metals: Effects of magnetization on the electric conductivity of nickel and of iron. Proc. R. Soc. Lond. 8, 546–550 (1856).

    ADS  Google Scholar 

  2. 2

    Campbell, I., Fert, A. & Jaoul, O. The spontaneous resistivity anisotropy in Ni-based alloys. J. Phys. C 3, S95–S101 (1970).

    ADS  Article  Google Scholar 

  3. 3

    McGuire, T. & Potter, R. Anisotropic magnetoresistance in ferromagnetic 3d alloys. IEEE Trans. Magn. 11, 1018–1038 (1975).

    ADS  Article  Google Scholar 

  4. 4

    Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472–2475 (1988).

    ADS  Article  Google Scholar 

  5. 5

    Binasch, G., Grünberg, P., Saurenbach, F. & Zinn, W. Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange. Phys. Rev. B 39, 4828–4830 (1989).

    ADS  Article  Google Scholar 

  6. 6

    Johnson, M. & Silsbee, R. H. Interfacial charge-spin coupling: Injection and detection of spin magnetization in metals. Phys. Rev. Lett. 55, 1790–1793 (1985).

    ADS  Article  Google Scholar 

  7. 7

    Jedema, F., Filip, A. & Van Wees, B. Electrical spin injection and accumulation at room temperature in an all-metal mesoscopic spin valve. Nature 410, 345–348 (2001).

    ADS  Article  Google Scholar 

  8. 8

    Johnson, M. & Silsbee, R. Thermodynamic analysis of interfacial transport and of the thermomagnetoelectric system. Phys. Rev. B 35, 4959–4972 (1987).

    ADS  Article  Google Scholar 

  9. 9

    Van Son, P., Van Kempen, H. & Wyder, P. Boundary resistance of the ferromagnetic-nonferromagnetic metal interface. Phys. Rev. Lett. 58, 2271–2273 (1987).

    ADS  Article  Google Scholar 

  10. 10

    Valet, T. & Fert, A. Theory of the perpendicular magnetoresistance in magnetic multilayers. Phys. Rev. B 48, 7099–7113 (1993).

    ADS  Article  Google Scholar 

  11. 11

    Maekawa, S., Valenzuela, S. O., Saitoh, E. & Kimura, T. Spin Current (Oxford Univ. Press, 2012).

    Google Scholar 

  12. 12

    Brataas, A., Bauer, G. E. & Kelly, P. J. Non-collinear magnetoelectronics. Phys. Rep. 427, 157–255 (2006).

    ADS  Article  Google Scholar 

  13. 13

    Sinova, J., Valenzuela, S. O., Wunderlich, J., Back, C. H. & Jungwirth, T. Spin Hall effect. Preprint at http://arxiv.org/abs/1411.3249 (2014).

  14. 14

    Miron, I. M. et al. Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection. Nature 476, 189–193 (2011).

    ADS  Article  Google Scholar 

  15. 15

    Liu, L. et al. Spin-torque switching with the giant spin Hall effect of tantalum. Science 336, 555–558 (2012).

    ADS  Article  Google Scholar 

  16. 16

    Garello, K. et al. Symmetry and magnitude of spin–orbit torques in ferromagnetic heterostructures. Nature Nanotech. 8, 587–593 (2013).

    ADS  Article  Google Scholar 

  17. 17

    Nakayama, H. et al. Spin Hall magnetoresistance induced by a nonequilibrium proximity effect. Phys. Rev. Lett. 110, 206601 (2013).

    ADS  Article  Google Scholar 

  18. 18

    Hahn, C. et al. Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta. Phys. Rev. B 87, 174417 (2013).

    ADS  Article  Google Scholar 

  19. 19

    Althammer, M. et al. Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids. Phys. Rev. B 87, 224401 (2013).

    ADS  Article  Google Scholar 

  20. 20

    Miao, B., Huang, S., Qu, D. & Chien, C. Physical origins of the new magnetoresistance in Pt/YIG. Phys. Rev. Lett. 112, 236601 (2014).

    ADS  Article  Google Scholar 

  21. 21

    Avci, C. O. et al. Fieldlike and antidamping spin–orbit torques in as-grown and annealed Ta/CoFeB/MgO layers. Phys. Rev. B 89, 214419 (2014).

    ADS  Article  Google Scholar 

  22. 22

    Hayashi, M., Kim, J., Yamanouchi, M. & Ohno, H. Quantitative characterization of the spin–orbit torque using harmonic Hall voltage measurements. Phys. Rev. B 89, 144425 (2014).

    ADS  Article  Google Scholar 

  23. 23

    Avci, C. O. et al. Interplay of spin–orbit torque and thermoelectric effects in ferromagnet/normal-metal bilayers. Phys. Rev. B 90, 224427 (2014).

    ADS  Article  Google Scholar 

  24. 24

    Kobs, A. et al. Anisotropic interface magnetoresistance in Pt/Co/Pt sandwiches. Phys. Rev. Lett. 106, 217207 (2011).

    ADS  Article  Google Scholar 

  25. 25

    Lu, Y. et al. Hybrid magnetoresistance in the proximity of a ferromagnet. Phys. Rev. B 87, 220409 (2013).

    ADS  Article  Google Scholar 

  26. 26

    Kim, J. et al. Layer thickness dependence of the current-induced effective field vector in Ta—CoFeB—MgO. Nature Mater. 12, 240–245 (2013).

    ADS  Article  Google Scholar 

  27. 27

    Weiler, M. et al. Local charge and spin currents in magnetothermal landscapes. Phys. Rev. Lett. 108, 106602 (2012).

    ADS  Article  Google Scholar 

  28. 28

    Kikkawa, T. et al. Longitudinal spin Seebeck effect free from the proximity Nernst effect. Phys. Rev. Lett. 110, 067207 (2013).

    ADS  Article  Google Scholar 

  29. 29

    Camley, R. E. & Barnaś, J. Theory of giant magnetoresistance effects in magnetic layered structures with antiferromagnetic coupling. Phys. Rev. Lett. 63, 664–667 (1989).

    ADS  Article  Google Scholar 

  30. 30

    Hood, R. Q. & Falicov, L. Boltzmann-equation approach to the negative magnetoresistance of ferromagnetic–normal-metal multilayers. Phys. Rev. B 46, 8287–8296 (1992).

    ADS  Article  Google Scholar 

  31. 31

    Zhang, W. et al. Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect. Appl. Phys. Lett. 103, 242414 (2013).

    ADS  Article  Google Scholar 

  32. 32

    Dyakonov, M. Magnetoresistance due to edge spin accumulation. Phys. Rev. Lett. 99, 126601 (2007).

    ADS  Article  Google Scholar 

  33. 33

    Dieny, B. Classical theory of giant magnetoresistance in spin-valve multilayers: Influence of thicknesses, number of periods, bulk and interfacial spin-dependent scattering. J. Phys. Condens. Matter 4, 8009–8020 (1992).

    ADS  Article  Google Scholar 

  34. 34

    Nguyen, H., Pratt, W. Jr & Bass, J. Spin-flipping in Pt and at Co/Pt interfaces. J. Magn. Magn. Mater. 361, 30–33 (2014).

    ADS  Article  Google Scholar 

  35. 35

    Valenzuela, S. O. & Tinkham, M. Direct electronic measurement of the spin Hall effect. Nature 442, 176–179 (2006).

    ADS  Article  Google Scholar 

  36. 36

    Zhang, S., Levy, P. & Fert, A. Conductivity and magnetoresistance of magnetic multilayered structures. Phys. Rev. B 45, 8689–8702 (1992).

    ADS  Article  Google Scholar 

  37. 37

    Haney, P. M., Lee, H-W., Lee, K-J., Manchon, A. & Stiles, M. Current induced torques and interfacial spin–orbit coupling: Semiclassical modeling. Phys. Rev. B 87, 174411 (2013).

    ADS  Article  Google Scholar 

  38. 38

    Manchon, A. & Zhang, S. Theory of nonequilibrium intrinsic spin torque in a single nanomagnet. Phys. Rev. B 78, 212405 (2008).

    ADS  Article  Google Scholar 

  39. 39

    Miron, I. M. et al. Current-driven spin torque induced by the Rashba effect in a ferromagnetic metal layer. Nature Mater. 9, 230–234 (2010).

    ADS  Article  Google Scholar 

  40. 40

    Mahfouzi, F., Nagaosa, N. & Nikolić, B. K. Spin-orbit coupling induced spin-transfer torque and current polarization in topological-insulator/ferromagnet vertical heterostructures. Phys. Rev. Lett. 109, 166602 (2012).

    ADS  Article  Google Scholar 

  41. 41

    Sánchez, D. & Büttiker, M. Magnetic-field asymmetry of nonlinear mesoscopic transport. Phys. Rev. Lett. 93, 106802 (2004).

    ADS  Article  Google Scholar 

  42. 42

    Rikken, G., Fölling, J. & Wyder, P. Electrical magnetochiral anisotropy. Phys. Rev. Lett. 87, 236602 (2001).

    ADS  Article  Google Scholar 

  43. 43

    Pop, F., Auban-Senzier, P., Canadell, E., Rikken, G. L. & Avarvari, N. Electrical magnetochiral anisotropy in a bulk chiral molecular conductor. Nature Commun. 5 (2014).

  44. 44

    Vera-Marun, I. J., Ranjan, V. & van Wees, B. J. Nonlinear detection of spin currents in graphene with non-magnetic electrodes. Nature Phys. 8, 313–316 (2012).

    ADS  Article  Google Scholar 

  45. 45

    Slachter, A., Bakker, F. L., Adam, J-P. & van Wees, B. J. Thermally driven spin injection from a ferromagnet into a non-magnetic metal. Nature Phys. 6, 879–882 (2010).

    ADS  Article  Google Scholar 

  46. 46

    Aziz, A. et al. Nonlinear giant magnetoresistance in dual spin valves. Phys. Rev. Lett. 103, 237203 (2009).

    ADS  Article  Google Scholar 

  47. 47

    Mellnik, A. et al. Spin-transfer torque generated by a topological insulator. Nature 511, 449–451 (2014).

    ADS  Article  Google Scholar 

  48. 48

    Fan, Y. et al. Magnetization switching through giant spin–orbit torque in a magnetically doped topological insulator heterostructure. Nature Mater. 13, 699–704 (2014).

    ADS  Article  Google Scholar 

  49. 49

    Olejník, K., Novák, V., Wunderlich, J. & Jungwirth, T. Electrical detection of magnetization reversal without auxiliary magnets. Phys. Rev. B 91, 180402(R) (2015).

    ADS  Article  Google Scholar 

Download references

Acknowledgements

This work was funded by the Swiss National Science Foundation (Grant No. 200021-153404) and the European Commission under the 7th Framework Program (SPOT project, Grant No. 318144).

Author information

Affiliations

Authors

Contributions

C.O.A., K.G. and P.G. planned the experiments; M.G., A.G., S.F.A. and C.O.A. carried out the sample growth and patterning; C.O.A., K.G. and A.G. performed the measurements; C.O.A. and P.G. analysed the data and wrote the manuscript. All authors contributed to the discussion of the data in the manuscript and Supplementary Information.

Corresponding authors

Correspondence to Can Onur Avci or Pietro Gambardella.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 741 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Avci, C., Garello, K., Ghosh, A. et al. Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers. Nature Phys 11, 570–575 (2015). https://doi.org/10.1038/nphys3356

Download citation

Further reading

Search

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing