Spin waves in three dimensions are observed for the first time

A study coordinated by the Politecnico di Milano published in Nature Communications

An international team of scientists from the Politecnico di Milano, the Paul Scherrer Institute (Switzerland) and the Max Planck Institute for Chemical Physics of Solids (Germany) has succeeded for the first time in reconstructing the three-dimensional structure of spin waves. 

The study, published in the journal Nature Communications, opens up new perspectives for the development of innovative technologies in the fields of spintronics and quantum computation. 

Spin waves are tiny oscillations of the magnetic moment ('spin') of electrons, which propagate in magnetic materials, such as iron, in a similar way as water waves propagate in a pond. Until now, however, directly observing their propagation in three dimensions has been an impossible task, resulting in the loss of much crucial information about their structure and their interactions within materials.

Today, researchers have managed to take lots of photographs of spin waves at various angles, rotating the magnetic sample as the photos were taken. Then with the images, using an ad-hoc algorithm, they reconstructed the complete three-dimensional structure of the spin waves for the first time.

What makes these measurements very complex is that spin waves are very small, on the order of a millionth of a millimetre, and very fast: they oscillate a billion times per second. To capture these blur-free images, you need a camera with an extremely fast shutter and a magnification capacity of millions of times. Today, the only machines capable of doing this are synchrotrons.

Thanks to this result, it will be possible to study the propagation and interaction of spin waves as never before, and in the near future it will be possible to design new devices that exploit the three-dimensionality of wave phenomena for classical and quantum computation.

The first author of the research is Davide Girardi, a PhD student in the PhyND research group in the Department of Physics of the Politecnico di Milano, led by Edoardo Albisetti and Daniela Petti. 

The research was funded by ERC Starting Grant B3YOND (no 948225) of the European Union's Horizon H2020 programme, coordinated by Edoardo Albisetti of the Physics Department of the Politecnico di Milano.

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