Spin-Phase Detector
The magnetic moments, or spins, in certain magnets can form spiral-shaped arrangements, which might be useful for storing information. Research on these so-called helimagnets has typically focused on the orientation of these spin arrangements, with “left-hand-turning” and “right-hand-turning” spirals serving as 0s and 1s. But the spin phase—a parameter describing the spin direction at one end of the helical pattern—might also be useful for storage purposes. Nan Jiang from Osaka University in Japan and his colleagues report on a new way to measure the spin phase [1]. The team’s spin-valve method might eventually be used to read and write information in a helimagnet device.
For a single helimagnet crystal, the spin phase can be recovered by measuring how the spins are pointing at the surface of the crystal. Such surface spins can be measured with x-ray spectroscopy and scanning tunneling microscopy, but these techniques are difficult to integrate into devices, Jiang says. He and his colleagues developed a more compatible method that could measure the spin phase electronically.
For their experiment, the researchers placed a chiral helimagnet (CrNb3S6) in contact with a copper wire that was designed to carry a current of spin-polarized electrons. As this spin current flowed past the helimagnet, it was partly absorbed—with the amount of absorption depending on the spin direction at the helimagnet surface. By measuring this spin-valve effect, the researchers could recover the spin phase of the helimagnet.
In the future, the team plans to electrically control the spin phase, using spin currents to write it as well as to read it. “Demonstrating such control would establish the spin phase as a practical information variable for low-power memory and logic,” Jiang says.
–Michael Schirber
Michael Schirber is a Corresponding Editor for Physics Magazine based in Lyon, France.
References
- N. Jiang et al., “Spin-phase detection by spin current in a chiral helimagnet,” Phys. Rev. B 112, L180402 (2025).