CPM Seminar

Controlling coherent spins with nanoscale addressability: Coupled dynamics of ferromagnetic vortices and individual nitrogen-vacancy spins

Jesse Berezovsky

Case Western Reserve University

A central obstacle impeding practical spintronics is the need for fast, local, strong (effective) magnetic fields to address, control, and couple spins on nanosecond timescales, in scalable nanometer-scale devices, at room temperature. Ferromagnetic vortices have the potential to overcome all of these issues. Soft ferromagnetic films patterned into disks or nanowires can exhibit vortex domain structure, with the vortex position controllable by small magnetic fields or electrical currents. The vortex core produces a dipole-like magnetic field, with strength approaching 1 T at the surface of the film. In a hybrid device, the vortex may be coupled to proximal electron spins, here, to nitrogen-vacancy (NV) spins in diamond. NV spins show significant promise for applications both in sensing and in quantum information processing. In either case, the ability to selectively control individual spins with nanoscale separation provides great advantage. In the former case, a dense ensemble of NVs can function as a high-resolution sensor array. In the latter case, nanometer-scale separation between NVs allows generation of entangled spin states via dipole-dipole coupling. Here, I will discuss recent results in which we study this coupled NV/vortex system [1]. By simultaneously measuring the vortex magnetization (via magneto-optical microscopy)[2] and the NV spin resonances (via optically-detected magnetic resonance), we observe a large NV spin splitting as we drive the vortex core into proximity with an NV. This large splitting implies a large magnetic field gradient, allowing for spin addressability with nanometer-scale resolution. We then show that the vortex core can be translated using fast magnetic field pulses, to sequentially address spins on ~100 ns timescales. These results also open up a number of interesting avenues to explore the physics of the coupled vortex/NV system, including the effects of vortex pinning, and the coupled coherent dynamics of the mesoscopic vortex with the single NV spin.

[1] M.S. Wolf, R. Badea, J. Berezovsky, arXiv:1510.07073, 2015
[2] R. Badea, J. Berezovsky, arXiv:1510.07059, 2015.