Regulating a novel DW oscillator with a steady frequency by changing the current density.

The dynamic behaviors of a domain wall (DW) pinned by a notch pair or a single notch with different notch depths are studied. It is found that, in a relatively large current density range, the oscillation frequency of the DW becomes frozen and independent of current density when pinned by a notch pair with a notch depth larger than 12 nm. The current density range for freezing the frequency can be tuned by the notch depth. A chain of notch pairs is designed to introduce more pinned DWs into the nanowire. By increasing the number of DWs and applying a proper magnetic field, the oscillation amplitude can be greatly enhanced. Our finding suggests that nanowires with a series of deep notch pairs may have an important application in the development of DW based spin-transfer nano-oscillators with a high tolerance for current fluctuation.