Physicists generate new nanoscale spin waves

Strong alternating magnetic fields can be used to generate a new type of spin wave previously predicted only theoretically. This was achieved for the first time by a team of physicists from the Martin Luther University Halle-Wittenberg (MLU). They report on their work in Nature communication and provide the first microscopic images of these spin waves.

The basic idea of ​​spintronics is to use a special property of electrons – spin – for various electronic applications such as data and information technology. Spin is the intrinsic angular momentum of electrons that produces a magnetic moment. Coupling these magnetic moments creates the magnetism that could ultimately be used in information processing. When these coupled magnetic moments are excited locally by a magnetic field pulse, these dynamics can propagate as waves throughout the material. These are called spin waves or magnons.

A special type of these waves is the core of the work of the physicists from Halle. Normally, the nonlinear excitation of magnons produces integers of the output frequency—1,000 megahertz becomes 2,000 or 3,000, for example.

“So far, it has only been theoretically predicted that nonlinear processes can generate spin waves at higher half-integer multiples of the excitation frequency,” explains Professor Georg Woltersdorf from the Department of Physics at MLU. The team has now been able to show experimentally what conditions are necessary to generate these waves and control their phase. Phase is the state of oscillation of a wave at a particular point and time. “We are the first to confirm these excitations in experiments and have even been able to map them,” says Woltersdorf.

According to the physicist, the waves can be generated in two stable phase states, which means that this discovery can potentially be used in data processing applications, since computers, for example, also use a binary system.

More information:
Rouven Dreyer et al., Imaging and Phase Locking of Nonlinear Spin Waves, Nature communication (2022). DOI: 10.1038/s41467-022-32224-0

Provided by Martin-Luther-Universität Halle-Wittenberg