MITの物理学者が新たな磁性現象を観測、スピントロニクス技術への応用に期待（Physicists observe new form of magnetism）

2025-06-05 マサチューセッツ工科大学(MIT)

Credits:Image: Courtesy of the researchers

＜関連情報＞

• https://news.mit.edu/2025/physicists-observe-new-form-magnetism-0605
• https://www.nature.com/articles/s41586-025-09034-7

p波磁石の電気的スイッチング Electrical switching of a p-wave magnet

Qian Song,Srdjan Stavrić,Paolo Barone,Andrea Droghetti,Daniil S. Antonenko,Jörn W. F. Venderbos,Connor A. Occhialini,Batyr Ilyas,Emre Ergeçen,Nuh Gedik,Sang-Wook Cheong,Rafael M. Fernandes,Silvia Picozzi & Riccardo Comin
Nature  Published:28 May 2025
DOI:https://doi.org/10.1038/s41586-025-09034-7

Abstract

Magnetic states with zero magnetization but non-relativistic spin splitting are outstanding candidates for the next generation of spintronic devices. Their electronvolt (eV)-scale spin splitting, ultrafast spin dynamics and nearly vanishing stray fields make them particularly promising for several applications^1,2. A variety of such magnetic states with non-trivial spin textures have been identified recently, including even-parity d-wave, g-wave or i-wave altermagnets and odd-parity p-wave magnets^3,4,5,6,7. Achieving voltage-based control of the non-uniform spin polarization of these magnetic states is of great interest for realizing energy-efficient and compact devices for information storage and processing^8,9. Spin-spiral type II multiferroics are optimal candidates for such voltage-based control, as they exhibit an inversion-symmetry-breaking magnetic order that directly induces ferroelectric polarization, allowing for symmetry-protected cross-control between spin chirality and polar order^{10,11,12,13,14}. Here we combine photocurrent measurements, first-principles calculations and group-theory analysis to provide direct evidence that the spin polarization of the spin-spiral type II multiferroic NiI₂ exhibits odd-parity character connected to the spiral chirality. The symmetry-protected coupling between chirality and polar order enables electrical control of a primarily non-relativistic spin polarization. Our findings represent an observation of p-wave magnetism in a spin-spiral type II multiferroic, which may lead to the development of voltage-based switching of non-relativistic spin polarization in compensated magnets.