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An international team of scientists is challenging the traditional concept of dividing magnetism into two branches in an article published in the journal Nature – the millennia-old ferromagnetic and the approximately century-old antiferromagnetic. Researchers, including Professor Ján Minár, Sunil Wilfred Dsouza, and Zdeněk Jansa from the New Technologies - Research Centre at the University of West Bohemia, have now experimentally demonstrated the existence of a third branch of magnetism called altermagnetism.

Usually, when we think of a magnet, we imagine a ferromagnet, which has a strong magnetic field, capable of holding, for example, a shopping list on the fridge. Its magnetic field arises from the alignment of the magnetic field of millions of its atoms in the same direction. This magnetic field can also be used to modulate electric current in IT components.

However, ferromagnetic fields represent a serious limitation in the spatial and temporal scalability of components. Thus, significant research attention in recent years has been directed towards the second, antiferromagnetic branch. Antiferromagnets are less known but much more common materials in nature, where the directions of atomic magnetic fields on neighboring atoms alternate, similar to the white and black colors on a chessboard. They do not create unwanted magnetic fields, but unfortunately, they are so anti-magnetic that they have not yet found application in IT.

The altermagnets, addressed in the Nature article, combine the advantages of ferromagnets and antiferromagnets, paving the way for innovations in the IT sector. While ferromagnetism and antiferromagnetism have limitations in practical IT usage, altermagnets bring new possibilities through the combination of the benefits of both forms of magnetism.

Professor Ján Minár from NTC describes the contribution of the research center in Plzeň. "We have long been focusing on research and discovering new functional materials with unexpected properties that emerge at the macroscopic level due to the interaction and organization of microscopic components, such as atoms or molecules of the material. I'm talking about properties like superconductivity, topological order, quantum entanglement, and precisely ferromagnetism. At the NTC research institute, we have a photoelectron emission spectrometer at our disposal, which allows us to examine the spin and angular resolution of materials. And it was precisely the spin symmetry that helped identify the unconventional magnetic phase referred to as altermagnetism," he says.

"The altermagnetic phase allows changes in how particles behave in materials without needing to have traditional magnetic properties. This concerns that Kramers' spin degeneracy, which is also in the title of the joint article in the journal Nature," adds Ján Minár.

Information about the new branch of magnetic materials emerged in 2020; the original theoretical predictions and the first indirect experimental confirmation were provided by the team from the Institute of Physics of the Czech Academy of Sciences and the University of Mainz.

Possible altermagnets have been identified among more than two hundred materials, ranging from insulators and semiconductors to metals and superconductors. Many of them were well-known and studied without identifying their altermagnetic nature. Altermagnetism has opened doors to new possibilities in research and its application, leading to significant interest from scientific teams worldwide. This has resulted in many new studies exploring altermagnetism and its potential for research and practice. However, direct experimental evidence of altermagnetism was lacking until this publication in the journal Nature.

Read a special comment in  the News and Views section.

For more details, refer to the press release by the Czech Academy of Sciences.

Cover image source: Czech Academy of Sciences, Libor Šmejkal, Anna Birk Hellenes