Stochastic nature of current-excited magnetic domain and domain wall dynamics microscopically investigated by Lorentz microscopy

We microscopically investigate the dynamics of magnetic domains and domain walls induced by a current pulse in Permalloy narrow wires by means of Lorentz microscopy and simultaneous transport measurement. A variety of magnetic domain and domain wall dynamics are induced as a function of current density flowing into the wire and wire resistance. Important finding is that observed magnetic domain wall displacement and domain nucleation explicitly exhibit stochastic nature, indicating that the magnetic state in the wire is hardly controlled by using solely the current pulse. However, the application of small in-plane magnetic field changes drastically the nature into deterministic, which effectively improves controllability of the magnetic domain and domain wall dynamics using current.