Evidence for out-of-easy-plane solitons in CsMnBr3 Academic Article uri icon

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abstract

  • CsMnBr3 is a quasi-one-dimensional antiferromagnetic insulator. The spin interactions are predominately of a Heisenberg nature, but at low temperatures the smaller dipolar interactions result in "easy-plane" one-dimensional antiferromagnetic ordering. We have examined the spin fluctuations at low energies, near the magnetic zone centre, with inelastic neutron scattering techniques. By means of a subtraction algorithm, we have separated intensities, as a function of the wave vector and energy, of the two polarizations of spin fluctuations (in-plane and out-of-plane). We report a strong qualitative difference between the energy dependence of the two polarizations, with the "out-of-plane" intensity exhibiting central-mode behaviour. A model of noninteracting Sine–Gordon solitons in the easy-plane antiferromagnet proposed by Mikeska provides an excellent qualitative and reasonable quantitative accounting of the polarization, wave vector, and energy dependence of the neutron scattering with low-energy transfer at 15 K. The model, however, cannot account for our elevated-temperature results. We have modified the theory using the phenomenological approach of ascribing an upwards renormalization of the soliton mass with temperature. The resulting comparison with our results is good.

publication date

  • September 1, 1985