The spin-torque effect in a nanomagnet. (top left) If the polarization of the spins in the current (ns, green arrow) is parallel to the easy axis (black arrow), the spin torque opposes the natural damping and opens up the angle of the precession cone at all points along the cone. (top right) If ns makes a finite angle with the easy axis, the spin torque opens the precession cone angle around a half circle centered at point Q, but closes the cone angle in the other half circle centered at point P. Applying two successive spin-torque pulses either both at point Q, or at points P and Q, increases or decreases the net effectiveness of the spin torque in inducing a dynamic switch. (bottom) Schematic of the nanopillar structure. The free layer is the right layer and the current is applied along the horizontal axis of the pillar. The polarization of the current (green arrows) also rotates as a result of the spin-torque effect.