Scientific Reports (Jun 2021)

Spin glass behavior and magnetic boson peak in a structural glass of a magnetic ionic liquid

  • Maiko Kofu,
  • Ryuta Watanuki,
  • Toshiro Sakakibara,
  • Seiko Ohira-Kawamura,
  • Kenji Nakajima,
  • Masato Matsuura,
  • Takeshi Ueki,
  • Kazuhiro Akutsu,
  • Osamu Yamamuro

DOI
https://doi.org/10.1038/s41598-021-91619-z
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 8

Abstract

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Abstract 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, C4mimFeCl4. Magnetization measurements demonstrate that an antiferromagnetic ordering occurs at T N = 2.3 K in the crystalline state, while a spin glass transition occurs at T SG = 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 SG and gradually disappeared above T SG. 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.