Computers, smartphones and data centres of the future could become faster and more efficient, while significantly reducing energy consumption. A key step toward this goal comes from a recent discovery in the field of magnetism, to which the University of Milano-Bicocca has made a major contribution. A team from the Department of Materials Science, led by Professor Silvia Picozzi, has identified a new material—nickel iodide (NiI₂)—which belongs to a recently discovered class known as altermagnets. The study, carried out in collaboration with the Massachusetts Institute of Technology (MIT), has been published in Nature, one of the world’s leading scientific journals.
Traditional magnetism theory distinguishes between two main categories of magnetic materials: ferromagnets (such as everyday magnets), which are easy to control but cannot be miniaturised beyond a certain limit; and antiferromagnets, which are more stable, faster, and immune to so-called "stray magnetic fields", but are hard to manipulate due to the absence of net magnetisation.
In 2022, a third form of magnetic behaviour was identified: altermagnetism. Altermagnets exhibit a completely new magnetic response, overcoming the limitations of both traditional types. Although they have no net magnetisation, the electronic states with opposite spin in these materials have different energies. This allows for more effective and precise control of magnetic behaviour.
Due to its enormous potential for future technologies, altermagnetism was recognised by Science as one of the top scientific breakthroughs of 2024—the only entry from the field of physics. These materials could play a crucial role in the development of spintronics, a next-generation electronics paradigm based on electron spin rather than just charge. This could lead to devices that are more precise, faster, smaller, and dramatically more energy-efficient. For example, some prototypes of spintronic RAM have already demonstrated energy savings of over 95% compared to conventional CMOS devices—a remarkable figure, especially considering that data centres currently account for more than 2% of global energy consumption.
In this project, the Milano-Bicocca team was responsible for the theoretical development and numerical simulations, while the MIT team carried out the material’s physical characterisation. Nickel iodide now stands as a key model system for studying altermagnets, though it currently requires extremely low temperatures to display its magnetic properties and is not yet usable in real-world devices.
The next step will be to build on the insights gained from NiI₂ to design new altermagnetic materials that are stable at room temperature. The ultimate goal: to enable the creation of ultra-efficient, high-performance electronic devices.
Figure – Helically arranged spins in NiI₂ are controlled by an electric field (top and bottom), leading to a change in the spin character of the electronic states (right column).