Leiden University Student Repository

Hubert, Michel (2018)

Using Josephson junctions as superconducting memory devices

Master thesis | Physics (MSc)

In this report, we discuss the possibility to use Josephson junctions as superconducting memory devices. These Josephson junctions are SFS (Superconductor-Ferromagnet-Superconductor) junctions. Due to a magnetization gradient, we generate triplet supercurrent at the interface. The junctions are disk-shaped, with cobalt on the bottom as the ferromagnet and niobium on top as the superconductor. Through the niobium, a trench is milled, to create the junction. The magnetization of the cobalt is circular in a pattern called a vortex. In the center the magnetization comes out of the plane. This is called the vortex core, and splits the junction into two channels. We can push this vortex core out with an in-plane field. By measuring out-of-plane interference patterns, we can calculate the spatial supercurrent distribution. By measuring such patterns with and without the vortex, we have shown that these SFS Josephson junctions can be used as superconducting memory devices.

superconductor

memory device

ferromagnet

Josephson junction

Author

Hubert, Michel

Faculty

Faculty of Science

Specialisation

QMO

Supervisors

Aarts, Jan

ECTS Credits

5

Language

en