  Two promising strategies for achieving efficient control of magnetization in
future magnetic memory and non-volatile spin logic devices are spin transfer
torque from spin polarized currents and voltage-controlled magnetic anisotropy
(VCMA). Spin transfer torque is in widespread development as the write
mechanism for next-generation magnetic memory, while VCMA offers the potential
of even better energy performance due to smaller Ohmic losses. Here we
introduce a 3-terminal magnetic tunnel junction (MTJ) device that combines both
of these mechanisms to achieve new functionality: gate-voltage-modulated spin
torque switching. This gating makes possible both more energy-efficient
switching and also improved architectures for memory and logic applications,
including a simple approach for making magnetic memories with a maximum-density
cross-point geometry that does not require a control transistor for every MTJ.
