Probing magnetization dynamics by time-resolved x-ray holography with extended references

Vortex closure domains are fascinating nanoscopic magnetic structures. As well as being exemplary model objects – in many ways the vortices behave like classical harmonic oscillators – they are versatile elementary components, which can perform a number of functions ranging from non-volatile high-density data storage to microwave generation. Here we demonstrate our recent studies of vortex structures in thin film permalloy elements and  spin-torque oscillators using a recently developed time-resolved soft x-ray imaging technique HERALDO, which can provide high spatial resolution as well as a high level of immunity to mechanical and thermal drifts. In particular, we demonstrate time-resolved imaging of the dynamics of domain walls in square Py elements, and how it affects the polarisation of the vortex core and its reversal.