Magnetic Octupoles Revolutionize High-Speed, Energy-Saving Memory

By RIKEN November 26, 2024

Collected at: https://scitechdaily.com/magnetic-octupoles-revolutionize-high-speed-energy-saving-memory/

Researchers reveal a way to use antiferromagnets to create data-storage devices without moving parts.

Scientists have transformed memory device technology by utilizing antiferromagnetic materials and magnetic octupoles, achieving high speeds and low power consumption, paving the way for smaller, more efficient devices.

Advanced Magnetic Memory

Physicists at RIKEN have shown a groundbreaking method to create ultrafast, energy-efficient memory devices by replacing traditional magnetic materials with innovative alternatives.

In standard hard disk drives, data is accessed by physically moving the magnetic disk. This mechanical movement not only slows down the process but also makes the system prone to wear and failure.

Advantages of Domain-Wall Devices

A more efficient solution involves using electrical currents to shift the boundaries between magnetic domains—tiny regions in a material where magnetic moments are consistently aligned. These “domain-wall devices” hold great potential for enabling faster, low-power memory systems without the need for mechanical parts.

“In the case of a hard disk drive, you have a small coil which has to be physically moved around,” explains Yoshichika Otani of the RIKEN Center for Emergent Matter Science. “But for devices based on domain walls, you don’t need any mechanical movement. Rather, the domain wall moves, and you can read and write information electrically without any mechanical motion.”

Challenges With Ferromagnetic Domains

Domain-wall devices have been investigated using ferromagnetic domains in which all the spins in a domain are parallel with each other. But these require high current densities to push the domain walls around, which results in high power consumptions. The domains also generate stray magnetic fields, which makes it challenging to cram a lot of them into a small space, making miniaturization difficult.

Antiferromagnetic domains in which the spins are arranged in alternating directions could overcome both these problems. But their low net magnetic fields are a double-edged sword—they are beneficial for miniaturization, but they make it difficult to manipulate and detect the domains.

Breakthrough in Antiferromagnetic Materials

Now, Otani and his co-workers have demonstrated a new approach for realizing domain-wall devices based on antiferromagnetic materials that overcomes this difficulty.

The secret to their approach was to use noncollinear antiferromagnets in which sublattice moments form cluster magnetic octupoles (Figure 1). This contrasts with the much more commonly used magnetic dipoles, which have two poles and resemble tiny bar magnets.

Using this structure, the team was able to accelerate domain walls to speeds of 750 meters per second using about a hundredth of the current density needed to move ferromagnet domain walls.

The findings came as a nice surprise to the team. “We weren’t confident that it would work with octupoles,” says Otani. “But it actually worked when we tried it, and so we were pleasantly surprised.”

Reference: “Current-driven fast magnetic octupole domain-wall motion in noncollinear antiferromagnets” by Mingxing Wu, Taishi Chen, Takuya Nomoto, Yaroslav Tserkovnyak, Hironari Isshiki, Yoshinobu Nakatani, Tomoya Higo, Takahiro Tomita, Kouta Kondou, Ryotaro Arita, Satoru Nakatsuji and Yoshichika Otani, 11 June 2024, Nature Communications.
DOI: 10.1038/s41467-024-48440-9