Dynamical property of YFeMnO4

In order to interpret abrupt changes of distributions of orientations andmagnitudes of hyperfine fields in Mössbauer measurements of⁵⁷Fe in YFeMnO₄, a model is proposed. The origin is assumed to be not static but dynamic. Fluctuating fields are caused by spins in a fully frustrated spin system, namely, a Heisenberg spin system on a triangular lattice in a two-dimensional antiferromagnet. Extending the stochastic theory for the fluctuation between two states to that among many states with a Gaussian distribution, we fit the spectra with three parameters, hyperfine fieldH_hf, correlation time _c, andwidth of fluctuating field , within a limited condition of =_c=1. Obtained results represent the characteristic features of Mössbauer spectra well, in spite of a simplified model.