  Thanks to its unique symmetry, the unidirectional spin Hall and
Rashba-Edelstein magnetoresistance (USRMR) is of great fundamental and
practical interest, particularly in the context of reading magnetization states
in two-terminal spin-orbit torque switching memory and logic devices. Recent
studies show that topological insulators could improve USRMR amplitude.
However, the topological insulator device configurations studied so far in this
context, namely ferromagnetic metal/topological insulator bilayers and
magnetically doped topological insulators, suffer from current shunting by the
metallic layer and low Curie temperature, respectively. Here, we report large
USRMR in a new material category - magnetic insulator/topological insulator
bi-layered heterostructures. Such structures exhibit USRMR that is about an
order of magnitude larger than the highest values reported so far in all-metal
Ta/Co bilayers. We also demonstrate current-induced magnetization switching
aided by an Oersted field, and electrical read out by the USRMR, as a prototype
memory device.
