The third branch of magnetism has been experimentally demonstrated in manganese telluride, opening up opportunities for new research directions.
A recent study published in Nature reveals that an international team of scientists has challenged the conventional division of magnetism into two types: ferromagnetism, known for thousands of years, and antiferromagnetism, identified roughly a century ago. The researchers have now successfully demonstrated, through direct experiments, a third type of magnetism—altermagnetism—which had been theoretically predicted by scientists from Johannes Gutenberg University Mainz and the Czech Academy of Sciences in Prague several years earlier.
Limitations of the previously known magnetic branches for information technologies
We usually think of a magnet as a ferromagnet, which has a strong magnetic field that keeps a shopping list on the door of a refrigerator or enables the function of an electric motor in an electric car. The magnetic field of a ferromagnet is created when the magnetic field of millions of its atoms is aligned in the same direction. This magnetic field can also be used to modulate the electric current in information technology (IT) components.
At the same time, however, the ferromagnetic field poses a serious limitation to the spatial and temporal scalability of the components. Thus, a significant research focus in recent years has been on the second, antiferromagnetic branch of magnets. Antiferromagnets are lesser known but much more common materials in nature, where the directions of the atomic magnetic fields on adjacent atoms are staggered like white and black colors on a chessboard. Thus, antiferromagnets as a whole do not create undesirable magnetic fields, but unfortunately, they are so antimagnetic that they have not yet found active applications in information technology.
Altermagnets combine “incompatible” advantages
Recently predicted altermagnets combine the advantages of ferromagnets and antiferromagnets, which were thought to be fundamentally incompatible, and also have other unique benefits not found in the other branches. Altermagnets can be thought of as magnetic arrangements where not only the atomic moments on neighboring atoms alternate, but also the orientation of the atoms in the crystal. Thus, altermagnets do not create a magnetic field on the outside, but the electrons inside feel a magnetic field that is effectively 1,000 times stronger than the field of the magnet on the fridge. These fields can modulate electric currents akin to ferromagnets and are thus potentially very attractive for applications in future ultrascalable nanoelectronics.
In addition, scientists have identified more than 200 candidate materials for altermagnetism with properties covering insulators, DOI: 10.1038/s41586-023-06907-7