Nanoscale imaging and control of a new type of magnetism

Altermagnets combine the best of both worlds of ferromagnets, which are your usual type of fridge magnets, and antiferromagnets, which have fascinating properties but are hard to control and read out. Their experimental discovery by the same consortium, but lead by the EPFL and the Paul Scherrer Institute (PSI), was published earlier this year and made it as runner-up in the Science breakthrough of the year 2024.

The promise of altermagnets lies in the fact that their read-out response is similar to ferromagnets, but that they have no stray magnetic field. This enables making smaller magnetic bits that can be switched at much higher frequencies and with less energy. In order to make the next step towards such applications it is essential to understand the domain structure and to find ways to control it. “In our previous work we measured the behaviour of the electrons and their spin in reciprocal space, but had no direct image of how they organise in real space” Prof. Hugo Dil says. In this new work the authors used the advanced imaging capabilities of the MaxIV synchrotron in Sweden to take nanoscale pictures of the spin orientation. “It was astonishing to see how the six possible domains come together at special points, called vortices or anti-vortices, and that we can move them around by magnetic fields” Hugo Dil continues. This opened the door to the next step of creating single domains by micro machining, which then behave like single magnetic bits.

The larger public will probably be impressed by structure and control of the domains and their potential for applications, but for the experts in the field it is also the fact that such high quality images can be obtained that is highly promising. “This highlights again the importance of developing new techniques and their availability at large scale research facilities or platforms” Prof. Dil concludes.