Superconductors and spin waves

Artistic representation of the setup of an experiment controlling spin waves travelingin YIG thin layers using superconductivity. Credit: Michael Borst, TU Delft
Representation of the experimental setup to study the effect of superconductivity on spin waves in YIG thin layers. Image courtesy: Michael Borst, TU Delft

Spin waves offer exciting opportunities for data manipulation since one can harness their wave nature for information processing. For such pursuit, it is essential to be able to make lenses, mirrors, cavities, or channels for these magnetic waves. Such devices require the ability to locally change the wavelength of the spin wave without damping or resistive effects.  By using NV magnetometry, Michael Borst (TU Delft, van der Sar Lab) and co-workers show that superconductors are great tools to manipulate spin waves.

A superconducting mirror

The team led by Prof. van der Sar fabricated a device where spin waves travel in Yttrium Iron Garnet (YIG). They placed a diamond membrane with NV centers on top to be able to image the spin waves. With this, they could observe that a stripe of molybdenum–rhenium (MoRe) modifies the wavelength of the spin waves once it turns superconducting when cooled down.

This is explained by the Meissner effect, by which superconductors expel magnetic fields from their interior. To do so, they generate currents that counter-act the applied field, the so-called Meissner-currents. The stray fields generated by a spin wave thus leads to Meissner currents in the superconductor, which in turn modifies the spin-wave, forming a hybrid spin-wave-Meissner-current mode. The wavelength of this mode as a function of external parameters such as magnetic field and temperature is then imaged by the NV centers. They also reveal how deep the magnetic field penetrates the superconductor, that is an alternative method to measure the London penetration depth.

If you want to dive deeper in these wonderful results obtained with wide field NV magnetometry, check out directly the Borst et al. paper published in Science in October 2023. We congratulate the team for such a groundbreaking research.

NV Magnetometry and spin waves

The work by M. Borst and co-workers highlights that NV magnetometry will play a crucial role in proving the functionality of such future spin-wave devices. The spin-waves used in this work have wavelengths in the micrometer-range, thus it was possible to image them using widefield NV magnetometry.

Diamond membranes similar to those used in this work for widefield NV magnetometry are provided by the Qnami Quantum Foundry. Qnami NV diamonds offer unparalleled capabilities for a variety of applications in a cost-effective and customizable manner. Learn more about the customizable NV diamonds on the Quantum Foundry page. 

To image sub-micron wavelengths or reveal the impact of nanoscale defects, Scanning NV Magnetometry would be the technology of choice. If you want to learn more about the possibility to image spin waves using Qnami ProteusQ, you can drop an email to Peter, our Application Scientist. He would be happy to talk about your research and explore together whether you could benefit from using ProteusQ for your applications. 

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