Hematite's Altermagnetism: A Breakthrough for Spintronic Technologies

Researchers at the Oak Ridge National Laboratory (ORNL) have identified a rare form of magnetism in hematite, an iron oxide commonly known as rust. This discovery provides experimental evidence of altermagnetism, a newly proposed third form of magnetism first introduced in 2022. Hematite's stability at temperatures exceeding 1,200 degrees Fahrenheit positions it as a suitable candidate for room-temperature spintronic applications, which traditionally require extensive cooling. Qiyang Sun, PhD, the project lead, emphasized the significance of this finding, stating, “By confirming its altermagnetic nature, we open a new platform for engineers to design high-speed, low-power quantum electronics using materials that are inexpensive and widely available.”

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Altermagnets differ from conventional magnets and antiferromagnets in that their electron spins align in opposite directions. This unique alignment allows for the flow of pure spin currents without electric charge, making altermagnets particularly advantageous for spintronic technologies. Spintronics leverages the spin of electrons for data processing and storage, potentially enabling devices that operate faster and consume less energy than current electronic technologies. However, the challenge has been identifying practical materials for these applications, a hurdle that the discovery of altermagnetism in hematite may help overcome.

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To validate hematite's altermagnetic properties, the ORNL team utilized the Spallation Neutron Source (SNS), a leading neutron research facility. They employed inelastic neutron scattering, a technique that allows researchers to probe the material's internal magnetic dynamics at the atomic level by observing energy changes in neutrons interacting with the sample. This method was crucial for detecting magnon splitting, a phenomenon indicative of altermagnetism, which cannot be observed through other experimental techniques. Sun noted, “Inelastic neutron scattering is the only method capable of resolving these fine spectral features.”

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The confirmation of altermagnetism in hematite suggests that this ubiquitous material could play a pivotal role in the next generation of high-speed, low-power quantum electronics. The researchers anticipate that utilizing charge-free spin currents could significantly reduce energy loss and heat generation, enhancing overall efficiency in electronic devices. Future investigations will focus on understanding how spin-wave gaps affect heat transport in hematite. The findings have been published in the journal *Physical Review Letters*, marking a significant step forward in the field of quantum magnetism.

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While the discovery is promising, some experts caution that practical applications of altermagnetism in commercial technologies may still face significant hurdles. The transition from experimental findings to real-world applications often involves complex challenges, including scalability and integration into existing systems.

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• “Hematite is abundant, chemically stable and nontoxic,” — Qiyang Sun, PhD, Project Lead, ORNL

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• “The confirmation of altermagnetism in hematite – a material as common as rust – demonstrates that a potential component for the next revolution in high-speed, low-power quantum electronics may already be all around us,” — Qiyang Sun, PhD, Project Lead, ORNL

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