Enhancing ferromagnets for high-speed technology

Auto-oscillations and spin inertia in ferromagnets.

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Researchers at the University of California, Riverside, and an international team have successfully harnessed ultra-fast spin behavior in ferromagnets. Their research, published in Physical Review Letters and recognized as an editor’s suggestion, opens pathways for applications operating at terahertz frequencies.

Today’s electronics run at gigahertz speeds, but this discovery could enable devices a thousand times faster using conventional ferromagnetic materials. Ferromagnets align electron spins and produce spin waves, which are essential for future technologies in computing and communication.

When spins oscillate, they encounter resistance from interactions with electrons and the crystal structure of the ferromagnet. These interactions also give spin inertia, causing another type of oscillation called nutation.

 Igor Barsukov, an associate professor of physics and astronomy, highlighted that nutation happens at extremely high frequencies, which is crucial for future computer and communication technologies. Physicists’ recent experimental confirmation of nutational oscillations has sparked enthusiasm in the magnetism research community.

Modern spintronic applications manipulate spins by injecting spin currents into the magnet.

Barsukov and his team discovered that injecting a spin current with the opposite sign can trigger nutational auto-oscillations. Coauthor Allison Tossounian, formerly an undergraduate in Barsukov’s group, highlighted the potential of these self-sustaining oscillations for future computing and communication technologies.

Barsukov explained that spin inertia introduces a second derivative in the motion equation, leading to some unexpected behaviors. They successfully synchronized dynamics driven by spin currents with spin inertia. They identified similarities between spin behaviors in ferromagnets and ferrimagnets.

This parallel could accelerate innovation by leveraging synergies between these fields. Materials with antiparallel spin lattices in ferrimagnets have recently garnered attention as candidates for high-speed applications.

Barsukov said, “But many technological challenges remain,” he said. “Our understanding of spin currents and materials engineering for ferromagnets has significantly advanced over the past few decades. Coupled with the recent confirmation of nutation, we saw an opportunity for ferromagnets to become excellent candidates for ultra-high frequency applications. Our study prepares the stage for concerted efforts to explore optimal materials and design efficient architectures to enable terahertz devices.”

Journal reference:

  1. Rodolfo Rodriguez, Mikhail Cherkasskii, et al., Spin Inertia and Auto-Oscillations in Ferromagnets. Physical Review Letters. DOI: 10.1103/PhysRevLett.132.246701.

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