November 07, 2022
Minneapolis, United States
Large unidirectional spin Hall and Rashba−Edelstein magnetoresistance in topological insulator/magnetic insulator heterostructures
The unidirectional spin Hall magnetoresistance (USMR) is initially discovered in ferromagnetic (FM) and normal metal (NM) structures1 and magnetic semiconductor structures2. It is a phenomenon observed in bilayer structures and is related to interfacial spin generation and scattering processes at the interface. The similar unidirectional spin Hall and Rashba-Edelstein magnetoresistance (USRMR) is observed in FM-topological insulator (TI) bilayers being much larger than that in FM-NM bilayers in bilayer structures3. They are of particular interest due to its potential of 180-degree sensitive electrical readout of magnetization in bilayer structures for spin-orbit torque switching devices.
Here, we report large unidirectional spin Hall and Rashba−Edelstein magnetoresistance in a new material family - magnetic insulator (MI)/TI Y3Fe5O12 (YIG)/Bi2Se3 bilayers. Such heterostructures exhibit a USRMR that is about an order of magnitude larger than the highest values reported in all-metal Ta/Co bilayers1. The polarized neutron reflectometry (PNR) reveals a unique temperature-dependent magnetic intermediary layer at the MI-substrate interface and a proximity layer at the MI-TI interface. These PNR findings echo the magnetoresistance results in a comprehensive physics picture. Finally, we demonstrate a prototype memory device based on a MI/TI bilayer, using USRMR for electrical read out of current-induced magnetization switching aided by a small Oersted field4.
References 1 C. O. Avci, K. Garello, A. Ghosh et al., Nat. Phys., vol. 11, no. 7, p. 570–575 (2015) 2 K. Olejník, V. Novák, J. Wunderlich et al., Phys. Rev. B - Condens. Matter Mater. Phys., vol. 91, no. 18, p. 180402 (2015) 3 Y. Lv et al., Nat. Commun., vol. 9, no. 1, p. 111 (2018) 4 Y. Lv et al., Appl. Phys. Rev., vol. 9, no. 1, p. 011406, (2022)