Researchers have determined that ultrathin ruthenium dioxide films possess the properties of an altermagnet—a material representing the third fundamental category of magnetism. This finding may lead to the development of quicker and more compact data storage devices.
Current magnetic memory technologies face fundamental limitations. Standard ferromagnets, which form the basis of hard drives and other storage units, allow for easy data writing via external magnetic fields. However, they are susceptible to outside magnetic interference, which causes errors and restricts data storage density.
Antiferromagnets are far more resistant to external disturbances, but they present a different issue: their internal magnetic spins mutually cancel out, making it extremely difficult to read stored data using electrical methods. Scientists have long sought materials that combine the magnetic stability of antiferromagnets with the ability for electrical reading and rewriting. Altermagnets promise precisely such a balance.
Ruthenium dioxide had long been regarded as a promising candidate for the role of an altermagnet; however, experimental results from various global laboratories differed significantly. The main hurdle was obtaining high-quality thin films with uniform crystal orientation.
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Scientists found a novel magnetic characteristic of ruthenium dioxide that could pave the way for faster and denser memory technologies
Scientists found a novel magnetic characteristic of ruthenium dioxide that could pave the way for faster and denser memory technologiesSource: AI/ScienceDaily.com
Physicists from Japan managed to overcome this obstacle. They grew ruthenium dioxide films with a single crystallographic orientation on sapphire substrates, carefully selecting the growth conditions. Then, using X-ray magnetic linear dichroism, specialists mapped the spin arrangement and magnetic order within the films. The measurements confirmed that the material’s net magnetization was zero—north and south poles mutually compensate, as expected for an altermagnet.
Concurrently, the scientists observed spin-dependent magnetoresistance: the electrical resistance of the films changed depending on the direction of electron spin. This served as electrical corroboration of the spin-split electronic structure—a key feature of altermagnets that distinguishes them from conventional antiferromagnets. The experimental data aligned with theoretical calculations, which definitively confirmed the material’s altermagnetic nature.
The obtained results open a path toward next-generation magnetic memory—one that is faster, more energy-efficient, and denser. The developed synchrotron analysis methods will also assist in finding and studying other altermagnetic materials, thereby accelerating the progress in spintronics and the electronics of the future.
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