Perpendicular spin torque promotes synchronization of magnetic tunnel junction based spin torque oscillators

We study how the perpendicular spin transfer torque term (bj), present in magnetic tunneling junctions (MTJs), affects the synchronization of serially connected MTJ-based spin torque oscillators (MTJ-STOs). We find that bj modifies the intrinsic preferred I-V phase shift in single MTJ-STO in such a way that serially connected MTJ-STOs synchronize much more readily without the need for additional circuitry to change the I-V phase. This result strongly suggests that synchronization of serially connected MTJ-STOs should be significantly more straightforward than the previously attempted serial synchronization of giant magnetoresistance based STOs (GMR-STOs).