  We demonstrate for the first time that functionally complete digital logic
can be created by using three terminal devices each consisting of a magnetic
tunnel junction (MTJ) and spin transfer torque (STT) element with a shared free
magnetic layer. Rather than the output of devices being high or low voltage
levels, logical states are represented as output resistances which retain their
state when unpowered. By cascading and clocking devices using a multi-phase
clock, threshold logic can be used to implement functionally complete digital
logic. Using this approach, a single device can act as an AND, NAND, OR, or NOR
gate without the need for external circuitry. Required device parameters and
tolerances are discussed.
