Domain-wall spin-torque resonators for frequency-selective operation

In this work we demonstrate control of the spin-torque resonance frequency of a domain wall (DW) in a notched wire through the lithographic engineering of the shape and profile of the notch. By modeling the magnetization dynamics of a current-driven domain wall in a nanometric constrained geometry, an almost harmonic pinning potential has been designed, and we experimentally demonstrate the operation of domain wall resonators with well-defined, selectable resonance frequencies, suitable for application in zero magnetic field. These results show that the DW may be treated to a good approximation as a quasiparticle acted on by a restoring force that may be derived from the notch shape in a physically transparent manner.