  A theoretical study of delayed feedback in spin-torque nano-oscillators is
presented. A macrospin geometry is considered, where self-sustained
oscillations are made possible by spin transfer torques associated with spin
currents flowing perpendicular to the film plane. By tuning the delay and
amplification of the self-injected signal, we identify dynamical regimes in
this system such as chaos, switching between precession modes with complex
transients, and oscillator death. Such delayed feedback schemes open up a new
field of exploration for such oscillators, where the complex transient states
might find important applications in information processing.
