  Ferromagnetic spin-valves and tunneling junctions are crucial for spintronics
applications and are one of the most fundamental spintronics devices. Motivated
by the potential unique advantages of antiferromagnets for spintronics, we
theoretically study here junctions built out of non-collinear antiferromagnets.
We demonstrate a large and robust magnetoresistance and spin-transfer torque
capable of ultrafast switching between parallel and anti-parallel states of the
junction. In addition, we show that the non-collinear order results in a
spin-transfer torque that is in several key aspects different from the
spin-transfer torque in ferromagnetic junctions.
