Large unidirectional spin Hall and Rashba-Edelstein magnetoresistance in topological insulator/magnetic insulator heterostructures

The unidirectional spin Hall and Rashba-Edelstein magnetoresistance is of great fundamental and practical interest, particularly in the context of reading magnetization states in two-terminal spin-orbit torque memory and logic devices due to its unique symmetry. Here, we report large unidirectional spin Hall and Rashba-Edelstein magnetoresistance in a new material family - magnetic insulator/topological insulator Y3Fe5O12/Bi2Se3 bilayers. Such heterostructures exhibit a unidirectional spin Hall and Rashba-Edelstein magnetoresistance that is about an order of magnitude larger than the highest values reported so far in all-metal Ta/Co bilayers. The polarized neutron reflectometry reveals a unique temperature-dependent magnetic intermediary layer at the magnetic insulator-substrate interface and a proximity layer at the magnetic insulator-topological insulator interface. These polarized neutron reflectometry findings echo the magnetoresistance results in a comprehensive physics picture. Finally, we demonstrate a prototype memory device based on a magnetic insulator/topological insulator bilayer, using unidirectional spin Hall and Rashba-Edelstein magnetoresistance for electrical readout of current-induced magnetization switching aided by a small Oersted field.