Theory of Spin Torque Switching Current for the Double Magnetic Tunnel Junction

A single-domain model for spin-transfer torque switching of double magnetic tunnel junctions with perpendicularly magnetized layers is developed. An analytical formula is derived for the switching current threshold, I
_c0
. Surprisingly, the model predicts that the switching current can be reduced by a factor of 10 compared to single magnetic tunnel junctions, for sufficiently large spin-polarizations. This effect is explained in terms of the “enhanced antiparallel-to-parallel” spin torque, familiar from single magnetic tunnel junctions.