We study the current-induced torques in asymmetric magnetic tunnel junctions containing a conventional ferromagnet and a magnetic Weyl semimetal contact. The Weyl semimetal hosts chiral bulk states and topologically protected Fermi arc surface states which were found to govern the voltage behavior and efficiency of current-induced torques. We report how bulk chirality dictates the sign of the nonequilibrium torques acting on the ferromagnet and discuss the existence of large fieldlike torques acting on the magnetic Weyl semimetal which exceed the theoretical maximum of conventional magnetic tunnel junctions. The latter are derived from the Fermi arc spin texture and display a counterintuitive dependence on the separation of the Weyl nodes. Our results shed light on the new physics of multilayered spintronic devices composed of magnetic Weyl semimetals, which might open doors for new energy-efficient spintronic devices.
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Acknowledgments. D.S., T.L., and J.P.W. were partially supported by the DARPA ERI FRANC program. T.L. and J.P.W. were also partially supported by the SMART, one of two nCORE research centers. F.X. acknowledges support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Physical Measurement Laboratory, Grant No. 70NANB14H209, through the University of Maryland.
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