  Magnetic torques generated through spin-orbit coupling promise
energy-efficient spintronic devices. It is important for applications to
control these torques so that they switch films with perpendicular
magnetizations without an external magnetic field. One suggested approach uses
magnetic trilayers in which the torque on the top magnetic layer can be
manipulated by changing the magnetization of the bottom layer. Spin currents
generated in the bottom magnetic layer or its interfaces transit the spacer
layer and exert a torque on the top magnetization. Here we demonstrate
field-free switching in such structures and attribute it to a novel spin
current generated at the interface between the bottom layer and the spacer
layer. The measured torque has a distinct dependence on the bottom layer
magnetization which is consistent with this interface-generated spin current
but not the anticipated bulk effects. This other interface-generated spin-orbit
torque will enable energy-efficient control of spintronic devices.
