Soliton Dynamics in Impure Ising-like Antiferromagnetic Chains

Abstract

Solitons in one-dimensional magnetic systems have recently been receiving considerable interest. The soliton behaves like a free particle when the mean free path λ is much longer than the inverse of the soliton density n_s (“coherent model”). On the contrary, if the condition n_sλ<<l holds due to scatterings from impurities or defects, the soliton moves diffusively (“incoherent model”). Experimetal evidence for such behavior was first presented with regard to the sine-Gordon soliton in TMMC doped with Cu²⁺ or Cd²⁺ by the ¹⁴N nuclear relaxation experiment by BOUCHER et al.[l]. The purpose of the present work is to study from the nuclear magnetic relaxation the behavior of the soliton (propagating domain boundary) in impure Ising-like antiferromagnetic chain of S=l/2 in the hexagonal compound CsCoCl₃. This compound exhibits successive phase transitions due to the frustration effect at T_N1=22K and T_N2=9K. Short range order is well developed above T_N1, and, in the intermediate phase (T_N2<T<T_N1), one-third of the magnetic chains still remain disordered. The presence of the coherent soliton in CsCoCl₃ for T>T_N2 has been shown by the experiments of ESR [2] and neutron scattering [3].