Kofu Maiko, Watanuki Ryuta, Sakakibara Toshiro, Ohira-Kawamura Seiko, Nakajima Kenji, Matsuura Masato, Ueki Takeshi, Akutsu Kazuhiro, Yamamuro Osamu
J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan.
Division of Materials Science and Chemical Engineering, Faculty of Engineering, Yokohama National University, Yokohama, Kanagawa, 240-8501, Japan.
Sci Rep. 2021 Jun 8;11(1):12098. doi: 10.1038/s41598-021-91619-z.
Glassy magnetic behavior has been observed in a wide range of crystalline magnetic materials called spin glass. Here, we report spin glass behavior in a structural glass of a magnetic ionic liquid, C4mimFeCl. Magnetization measurements demonstrate that an antiferromagnetic ordering occurs at T = 2.3 K in the crystalline state, while a spin glass transition occurs at T = 0.4 K in the structural glass state. In addition, localized magnetic excitations were found in the spin glass state by inelastic neutron scattering, in contrast to spin-wave excitations in the ordered phase of the crystalline sample. The localized excitation was scaled by the Bose population factor below T and gradually disappeared above T. This feature is highly reminiscent of boson peaks commonly observed in structural glasses. We suggest the "magnetic" boson peak to be one of the inherent dynamics of a spin glass state.
在被称为自旋玻璃的多种晶体磁性材料中都观察到了玻璃态磁性行为。在此,我们报道了磁性离子液体C4mimFeCl的结构玻璃中的自旋玻璃行为。磁化测量表明,在晶体状态下,反铁磁有序在T = 2.3 K时出现,而在结构玻璃状态下,自旋玻璃转变在T = 0.4 K时发生。此外,通过非弹性中子散射在自旋玻璃态中发现了局域磁激发,这与晶体样品有序相中自旋波激发形成对比。局域激发在低于T时按玻色子占据因子进行标度,在高于T时逐渐消失。这一特征与结构玻璃中常见的玻色子峰高度相似。我们认为“磁性”玻色子峰是自旋玻璃态的固有动力学之一。