Discovery of new third class of magnetism

Scientists have discovered the existence of a Third Form of Magnetism that could transform digital devices

A new class of magnetism called altermagnetism has been imaged for the first time in a new study. The findings could lead to the development of new magnetic memory devices with the potential to increase operation speeds of up to a thousand times. Scientists have created, manipulated and imaged an altermagnetic material for the first time. This theorized material has likely existed forever, but now we can tune and measure it directly. Electron spin patterns affect electronic fields like solid state hard drives and superconductors. Scientists have recently crafted and taken images of a novel new magnetic substance known as an altermagnetic material. While some discoveries are theorized decades before scientists can finally make or observe them, altermagnetism has arrived in the collective scientific consciousness over just a few years. And now, in a new study, scientists show that they can tune these materials very precisely in order to create specific directions of magnetism. 

Altermagnetism is a distinct form of magnetic order where the tiny constituent magnetic building blocks align antiparallel to their neighbours but the structure hosting each one is rotated compared to its neighbours. In fact, scientists have been able to confirm a wild (but substantiated) theory, that altermagnetism could combine regular ferromagnetism with antiferromagnetism. While it might not have much impact on your refrigerator magnet collection, for people who make superconductors and topological materials at near-absolute zero, this could be the next big thing. Standard ferromagnetic materials work by exercising a force on nearby objects made of iron or other qualifying elements and alloys. On the flip side, antiferromagnetism describes how these magnets can act in a very mild and almost invisible way on materials that don’t fall under the “ferrous” umbrella. And electromagnets, made by running a current through a coiled wire, work the same way, but more powerfully and while depending on that electrical current. Earth has a magnetic field in part because its spinning, molten metal core acts like an electromagnet.

Scientists have shown that this new third class of magnetism exists and can be controlled in microscopic devices. In an altermagnet, however, the direction of spin (which influences magnetism) can vary on the “grid” formed by what’s known as an ideal crystal, a material whose crystal patterns are perfect and not interrupted by faults, directional changes or a host of other things which can all happen naturally. Many natural diamonds are ideal crystals, which is part of what gives them their extremely clear appearance. But metals can be ideal crystals as well. In this experiment, the scientists used photoemission electron microscopy (PEEM), polarized in order to help reveal magnetic influence, to map the entire grid structure of crystalline manganese telluride (MnTe). Their combined visual showed the underlying crystal structure, with a grid of arrows indicating the directions of magnetism at each point. The scientists were also able to manipulate the points of magnetic spin.

Professor Peter Wadley, who led the research, explains: "Altermagnets consist of magnetic moments that point antiparallel to their neighbours. However, each part of the crystal hosting these tiny moments is rotated with respect to its neighbours. This is like antiferromagnetism with a twist! But this subtle difference has huge ramifications." Researchers first showed experimental evidence of altermagnetism in research published earlier this year, but they didn’t image the resulting material in this much detail. In the experiment, the researchers used a momentum microscope focused on a special area above the material which shows how its different electrons are spinning, the vital factor that determines how magnetism works. This work was another important step toward imaging the altermagnets in action.

Magnetic materials are used in the majority of long term computer memory and the latest generation of microelectronic devices. This is not only a massive and vital industry but also a significant source of global carbon emissions. Replacing the key components with altermagnetic materials would lead to huge increases in speed and efficiency while having the potential to massively reduce our dependency on rare and toxic heavy elements needed for conventional ferromagnetic technology. Nanomaterials in general are of high interest in many fields of research. Quantum computers operate on this level, and still have a ways to go before they’re practical outside of extremely specific and highly controlled lab settings. Altermagnetic materials may also revolutionize a field called spintronics, which refers to the study and optimization of solid state devices, including solid state drives (SSDs) in computers and smartphones, which make use of electron spin. While the traditional ferromagnets we use today are fine in many ways, they aren’t ideal, and can introduce a blurring between separated bits of data known as crosstalk.

Altermagnets combine the favourable properties of ferromagnets and antiferromagnets into a single material. They have the potential to lead to a thousand fold increase in speed of microelectronic components and digital memory while being more robust and efficient. Senior Research Fellow, Oliver Amin led the experiment and is co-author on the study, said: "Our experimental work has provided a bridge between theoretical concepts and real-life realisation, which hopefully illuminates a path to developing altermagnetic materials for practical applications." On a nano level, everything we store inside our devices is the result of the coordinated action of electrons. If these materials could be improved, it could mean higher efficiency, more storage within the same size of material, and less loss when data is accessed. The new experimental study was carried out at the MAX IV international facility in Sweden. The facility, which looks like a giant metal doughnut, is an electron accelerator, called a synchrotron, that produces x-rays. X-rays are shone onto the magnetic material and the electrons given off from the surface are detected using a special microscope. This allows an image to be produced of the magnetism in the material with resolution of small features down to the nanoscale. Scientists concluded that altermagnets could help to further the study of practical superconductors and topological materials. It seems the future of electronics could rely on highly customized spin patterns.

PhD student, Alfred Dal Din, has been exploring altermagnets for the last two years. This is yet another breakthrough that he has seen during his project. He comments: 'To be amongst the first to see the effect and properties of this promising new class of magnetic materials during my PhD has been an immensely rewarding and challenging privilege.'