Gen Masaki, Ikeda Akihiko, Aoyama Kazushi, Jeschke Harald O, Ishii Yuto, Ishikawa Hajime, Yajima Takeshi, Okamoto Yoshihiko, Zhou Xuguang, Nakamura Daisuke, Takeyama Shojiro, Kindo Koichi, Matsuda Yasuhiro H, Kohama Yoshimitsu
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan.
Proc Natl Acad Sci U S A. 2023 Aug 15;120(33):e2302756120. doi: 10.1073/pnas.2302756120. Epub 2023 Aug 7.
The mutual coupling of spin and lattice degrees of freedom is ubiquitous in magnetic materials and potentially creates exotic magnetic states in response to the external magnetic field. Particularly, geometrically frustrated magnets serve as a fertile playground for realizing magnetic superstructure phases. Here, we observe an unconventional two-step magnetostructural transition prior to a half-magnetization plateau in a breathing pyrochlore chromium spinel by means of state-of-the-art magnetization and magnetostriction measurements in ultrahigh magnetic fields available up to 600 T. Considering a microscopic magnetoelastic theory, the intermediate-field phase can be assigned to a magnetic superstructure with a three-dimensional periodic array of 3-up-1-down and canted 2-up-2-down spin molecules. We attribute the emergence of the magnetic superstructure to a unique combination of the strong spin-lattice coupling and large breathing anisotropy.
自旋与晶格自由度的相互耦合在磁性材料中普遍存在，并可能响应外部磁场而产生奇异的磁态。特别是，几何阻挫磁体是实现磁超结构相的理想平台。在此，我们通过在高达600 T的超高磁场中进行的先进磁化和磁致伸缩测量，观察到了呼吸型焦绿石铬尖晶石在半磁化平台之前出现的非常规两步磁结构转变。考虑到微观磁弹性理论，中间场相可归因于具有3上1下和倾斜2上2下自旋分子的三维周期性阵列的磁超结构。我们将磁超结构的出现归因于强自旋-晶格耦合和大呼吸各向异性的独特组合。
