Spin dynamics in natural multiferroic pyroxene NaFeSiO

天然マルチフェロイイック輝石NaFeSiOのスピンダイナミクス

Prokhnenko, O.*; Nikitin, S. E.*; 金子 耕士   ; 田端 千紘; 廣瀬 雄介; 常盤 欣文  ; 芳賀 芳範   ; 藤田 全基; 野尻 浩之*; Anovitz, L. M.*; Podlesnyak, A.*

Prokhnenko, O.*; Nikitin, S. E.*; Kaneko, Koji; Tabata, Chihiro; Hirose, Yusuke; Tokiwa, Yoshifumi; Haga, Yoshinori; Fujita, Masaki; Nojiri, Hiroyuki*; Anovitz, L. M.*; Podlesnyak, A.*

The spin dynamics in the natural mineral aegirine, NaFeSiO, which exhibits multiferroic properties, was studied using elastic and inelastic neutron scattering. Magnetism in pyroxenes arises from competing intra- and interchain exchanges that stabilize a variety of commensurate and incommensurate states. The incommensurate helical ground state remains robust, with no metamagnetic transitions observed and only gradual spectral changes under field. A phase diagram constructed in terms of the exchange ratios and captures the transition between commensurate and incommensurate regimes and unifies magnetic behavior across different pyroxenes. Despite structural variations ( vs ), the exchange topology and resulting magnetic frustration are closely related. These results establish NaFeSiO as a benchmark for understanding exchange-driven magnetism and field-stable spin dynamics in pyroxenes with three-dimensional magnetic coupling.