p波磁性体と呼ばれる新しいタイプの磁性体を実現～電流を用いた高効率な磁化制御などへ期待～

2025-10-23 理化学研究所,東京大学,高エネルギー加速器研究機構,J-PARCセンター,総合科学研究機構,日本原子力研究開発機構,科学技術振興機構

p波磁性体の磁気構造（左）と電子の運動方向に依存するスピン分裂（右）

＜関連情報＞

• https://www.riken.jp/press/2025/20251023_1/index.html
• https://www.nature.com/articles/s41586-025-09633-4

整合スピンヘリックスを持つ金属p波磁石 A metallic p-wave magnet with commensurate spin helix

Rinsuke Yamada,Max T. Birch,Priya R. Baral,Shun Okumura,Ryota Nakano,Shang Gao,Motohiko Ezawa,Takuya Nomoto,Jan Masell,Yuki Ishihara,Kamil K. Kolincio,Ilya Belopolski,Hajime Sagayama,Hironori Nakao,Kazuki Ohishi,Takashi Ohhara,Ryoji Kiyanagi,Taro Nakajima,Yoshinori Tokura,Taka-hisa Arima,Yukitoshi Motome,Moritz M. Hirschmann & Max Hirschberger
Nature  Published:22 October 2025
DOI:https://doi.org/10.1038/s41586-025-09633-4

Abstract

Antiferromagnetic states with a spin-split electronic structure give rise to spintronic, magnonic and electronic phenomena despite (near-)zero net magnetization^{1,2,3,4,5,6,7}. The simplest odd-parity spin splitting—p wave—was originally proposed to emerge from a collective instability in interacting electron systems^8,9,10,11,12. Recent theory has identified a distinct route to realize p-wave spin-split electronic bands without strong correlations^13,14, termed p-wave magnetism. Here we demonstrate an experimental realization of a metallic p-wave magnet. The odd-parity spin splitting of delocalized conduction electrons arises from their coupling to an antiferromagnetic texture of localized magnetic moments: a coplanar spin helix whose magnetic period is an even multiple of the chemical unit cell, as revealed by X-ray scattering experiments. This texture breaks space-inversion symmetry but approximately preserves time-reversal symmetry up to a half-unit-cell translation—thereby fulfilling the symmetry conditions for p-wave magnetism. Consistent with theoretical predictions, our p-wave magnet shows a characteristic anisotropy in the electronic conductivity^13,14,15. Relativistic spin–orbit coupling and a tiny spontaneous net magnetization further break time-reversal symmetry, resulting in a giant anomalous Hall effect (Hall conductivity >600 S cm⁻¹, Hall angle >3%), for an antiferromagnet. Our model calculations show that the spin-nodal planes found in the electronic structure of p-wave magnets are readily gapped by a small perturbation to induce the anomalous Hall effect. We establish metallic p-wave magnets as an ideal platform to explore the functionality of spin-split electronic states in magnets, superconductors, and in spintronic devices.