Magnetization switching through giant spin–orbit torque in a magnetically doped topological insulator heterostructure

Abstract

Recent demonstrations of magnetization switching induced by in-plane current in heavy metal/ferromagnetic heterostructures (HMFHs) have drawn great attention to spin torques arising from large spin–orbit coupling (SOC). Given the intrinsic strong SOC, topological insulators (TIs) are expected to be promising candidates for exploring spin–orbit torque (SOT)-related physics. Here we demonstrate experimentally the magnetization switching through giant SOT induced by an in-plane current in a chromium-doped TI bilayer heterostructure. The critical current density required for switching is below 8.9 × 104 A cm−2 at 1.9 K. Moreover, the SOT is calibrated by measuring the effective spin–orbit field using second-harmonic methods. The effective field to current ratio and the spin-Hall angle tangent are almost three orders of magnitude larger than those reported for HMFHs. The giant SOT and efficient current-induced magnetization switching exhibited by the bilayer heterostructure may lead to innovative spintronics applications such as ultralow power dissipation memory and logic devices.

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Figure 1: Experimental set-up and magnetic properties of the (Bi0.5Sb0.5)2Te3/(Cr0.08Bi0.54Sb0.38)2Te3 bilayer heterostructure.
Figure 2: Magnetization switching due to the SOT induced by an in-plane d.c. current.
Figure 3: Second-harmonic AHE resistance as a function of the in-plane external magnetic field.
Figure 4: Harmonic signals and effective spin–orbit fields obtained from the rotation experiments.

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Acknowledgements

We are grateful for the support from the DARPA Meso programme under contract No. N66001-12-1-4034 and N66001-11-1-4105. We also acknowledge the support from the Western Institute of Nanoelectronics (WIN) and the support from the FAME Center, one of six centres of STARnet, a Semiconductor Research Corporation programme sponsored by MARCO and DARPA. P.U., X.K. and M.L. acknowledge partial support from the Qualcomm Innovation Fellowship.

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Y.F., P.U., X.K. and K.L.W. conceived and designed the research. X.K. and L.H. grew the material. M.L. fabricated the Hall bar devices. Y.F., P.U. and X.K. performed the measurements. M.L., Z.W., J.T., L.H., L-T.C., M.M., G.Y., W.J., T.N. and R.N.S. contributed to the measurements and analysis. X.K. and T.N. performed structural analysis. Y.F., P.U., S.T. and Y.T. designed the theoretical model. Y.F., P.U., X.K. and K.L.W. wrote the paper with help from all of the other co-authors.

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Correspondence to Yabin Fan or Liang He or Kang L. Wang.

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The authors declare no competing financial interests.

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Fan, Y., Upadhyaya, P., Kou, X. et al. Magnetization switching through giant spin–orbit torque in a magnetically doped topological insulator heterostructure. Nature Mater 13, 699–704 (2014). https://doi.org/10.1038/nmat3973

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