该研究团队在高达600 T的超高磁场中，通过先进的磁化和磁致伸缩测量技术，观察到在呼吸烧绿石铬尖晶石中发生了非常规的两步磁结构转变。在半磁化平台之前，这一转变涉及微观磁弹性理论的中间场相位，可以分配给具有3-上-1-下和倾斜2-上-2-下自旋分子三维周期阵列的磁超结构。研究人员将这种磁性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。
据悉，自旋自由度和晶格自由度的相互耦合在磁性材料中是普遍存在的，这一现象可能在响应外部磁场时产生奇异的磁态。特别是，几何上受挫的磁体为实现磁性超结构相提供了肥沃的实验场，为进一步研究磁性材料的特性和应用提供了可能性。
附：英文原文
Title: Signatures of a magnetic superstructure phase induced by ultrahigh magnetic fields in a breathing pyrochlore antiferromagnet
Author: 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
Issue&Volume: 2023-8-7
Abstract: 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.
DOI: 10.1073/pnas.2302756120
Source: https://www.pnas.org/doi/10.1073/pnas.2302756120