Unidirectional spin-Hall and Rashba−Edelstein magnetoresistance in topological insulator-ferromagnet layer heterostructures

• Published in: Nature communications Vol. 9; no. 1; p. 111
• Main Authors: Lv, Yang, Kally, James, Zhang, Delin, Lee, Joon Sue, Jamali, Mahdi, Samarth, Nitin, Wang, Jian-Ping
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09-01-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 142/126; 639/166/987; 639/766/1130/2798; 639/925/357/997; Ferromagnetism; Figure of merit; Geometry; Heavy metals; Heterostructures; Humanities and Social Sciences; Magnetic moments; Magnetoresistance; Magnetoresistivity; Memory devices; multidisciplinary; Science; Science (multidisciplinary); Spintronics; Tantalum; Topological insulators
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-017-02491-3

The large spin−orbit coupling in topological insulators results in helical spin-textured Dirac surface states that are attractive for topological spintronics. These states generate an efficient spin−orbit torque on proximal magnetic moments. However, memory or logic spin devices based upon such switching require a non-optimal three-terminal geometry, with two terminals for the writing current and one for reading the state of the device. An alternative two-terminal device geometry is now possible by exploiting the recent discovery of the unidirectional spin Hall magnetoresistance in heavy metal/ferromagnet bilayers and unidirectional magnetoresistance in magnetic topological insulators. Here, we report the observation of such unidirectional magnetoresistance in a technologically relevant device geometry that combines a topological insulator with a conventional ferromagnetic metal. Our devices show a figure of merit (magnetoresistance per current density per total resistance) that is more than twice as large as the highest reported values in all-metal Ta/Co bilayers.
Unidirectional spin Hall magnetoresistance enables the new spintronic devices but is limited by the low amplitude or working temperature. Here, the authors report the large unidirectional spin Hall magnetoresistance in a topological insulator and ferromagnetic metal bilayer system at relatively higher temperature.