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.
This is a preview of subscription content
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
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).
Campbell, I., Fert, A. & Jaoul, O. The spontaneous resistivity anisotropy in Ni-based alloys. J. Phys. C 3, S95–S101 (1970).
McGuire, T. & Potter, R. Anisotropic magnetoresistance in ferromagnetic 3d alloys. IEEE Trans. Magn. 11, 1018–1038 (1975).
Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472–2475 (1988).
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).
Johnson, M. & Silsbee, R. H. Interfacial charge-spin coupling: Injection and detection of spin magnetization in metals. Phys. Rev. Lett. 55, 1790–1793 (1985).
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).
Johnson, M. & Silsbee, R. Thermodynamic analysis of interfacial transport and of the thermomagnetoelectric system. Phys. Rev. B 35, 4959–4972 (1987).
Van Son, P., Van Kempen, H. & Wyder, P. Boundary resistance of the ferromagnetic-nonferromagnetic metal interface. Phys. Rev. Lett. 58, 2271–2273 (1987).
Valet, T. & Fert, A. Theory of the perpendicular magnetoresistance in magnetic multilayers. Phys. Rev. B 48, 7099–7113 (1993).
Maekawa, S., Valenzuela, S. O., Saitoh, E. & Kimura, T. Spin Current (Oxford Univ. Press, 2012).
Brataas, A., Bauer, G. E. & Kelly, P. J. Non-collinear magnetoelectronics. Phys. Rep. 427, 157–255 (2006).
Sinova, J., Valenzuela, S. O., Wunderlich, J., Back, C. H. & Jungwirth, T. Spin Hall effect. Preprint at http://arxiv.org/abs/1411.3249 (2014).
Miron, I. M. et al. Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection. Nature 476, 189–193 (2011).
Liu, L. et al. Spin-torque switching with the giant spin Hall effect of tantalum. Science 336, 555–558 (2012).
Garello, K. et al. Symmetry and magnitude of spin–orbit torques in ferromagnetic heterostructures. Nature Nanotech. 8, 587–593 (2013).
Nakayama, H. et al. Spin Hall magnetoresistance induced by a nonequilibrium proximity effect. Phys. Rev. Lett. 110, 206601 (2013).
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).
Althammer, M. et al. Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids. Phys. Rev. B 87, 224401 (2013).
Miao, B., Huang, S., Qu, D. & Chien, C. Physical origins of the new magnetoresistance in Pt/YIG. Phys. Rev. Lett. 112, 236601 (2014).
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).
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).
Avci, C. O. et al. Interplay of spin–orbit torque and thermoelectric effects in ferromagnet/normal-metal bilayers. Phys. Rev. B 90, 224427 (2014).
Kobs, A. et al. Anisotropic interface magnetoresistance in Pt/Co/Pt sandwiches. Phys. Rev. Lett. 106, 217207 (2011).
Lu, Y. et al. Hybrid magnetoresistance in the proximity of a ferromagnet. Phys. Rev. B 87, 220409 (2013).
Kim, J. et al. Layer thickness dependence of the current-induced effective field vector in Ta—CoFeB—MgO. Nature Mater. 12, 240–245 (2013).
Weiler, M. et al. Local charge and spin currents in magnetothermal landscapes. Phys. Rev. Lett. 108, 106602 (2012).
Kikkawa, T. et al. Longitudinal spin Seebeck effect free from the proximity Nernst effect. Phys. Rev. Lett. 110, 067207 (2013).
Camley, R. E. & Barnaś, J. Theory of giant magnetoresistance effects in magnetic layered structures with antiferromagnetic coupling. Phys. Rev. Lett. 63, 664–667 (1989).
Hood, R. Q. & Falicov, L. Boltzmann-equation approach to the negative magnetoresistance of ferromagnetic–normal-metal multilayers. Phys. Rev. B 46, 8287–8296 (1992).
Zhang, W. et al. Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect. Appl. Phys. Lett. 103, 242414 (2013).
Dyakonov, M. Magnetoresistance due to edge spin accumulation. Phys. Rev. Lett. 99, 126601 (2007).
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).
Nguyen, H., Pratt, W. Jr & Bass, J. Spin-flipping in Pt and at Co/Pt interfaces. J. Magn. Magn. Mater. 361, 30–33 (2014).
Valenzuela, S. O. & Tinkham, M. Direct electronic measurement of the spin Hall effect. Nature 442, 176–179 (2006).
Zhang, S., Levy, P. & Fert, A. Conductivity and magnetoresistance of magnetic multilayered structures. Phys. Rev. B 45, 8689–8702 (1992).
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).
Manchon, A. & Zhang, S. Theory of nonequilibrium intrinsic spin torque in a single nanomagnet. Phys. Rev. B 78, 212405 (2008).
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).
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).
Sánchez, D. & Büttiker, M. Magnetic-field asymmetry of nonlinear mesoscopic transport. Phys. Rev. Lett. 93, 106802 (2004).
Rikken, G., Fölling, J. & Wyder, P. Electrical magnetochiral anisotropy. Phys. Rev. Lett. 87, 236602 (2001).
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).
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).
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).
Aziz, A. et al. Nonlinear giant magnetoresistance in dual spin valves. Phys. Rev. Lett. 103, 237203 (2009).
Mellnik, A. et al. Spin-transfer torque generated by a topological insulator. Nature 511, 449–451 (2014).
Fan, Y. et al. Magnetization switching through giant spin–orbit torque in a magnetically doped topological insulator heterostructure. Nature Mater. 13, 699–704 (2014).
Olejník, K., Novák, V., Wunderlich, J. & Jungwirth, T. Electrical detection of magnetization reversal without auxiliary magnets. Phys. Rev. B 91, 180402(R) (2015).
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).
The authors declare no competing financial interests.
About this article
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
Nature Communications (2022)
Communications Materials (2021)
Unidirectional spin Hall magnetoresistance in epitaxial Cr/Fe bilayer from electron-magnon scattering
Communications Physics (2021)
High spin mixing conductance and spin interface transparency at the interface of a Co2Fe0.4Mn0.6Si Heusler alloy and Pt
NPG Asia Materials (2021)
Nature Communications (2021)