ESR Study of the Normal-Incommensurate Phase Transition in Sr₂Nb₂O₇

Abstract

Temperature dependence of ESR line shape associated with Fe³⁺ in Sr₂Nb₂O₇ has been studied. The line shape is analyzed in terms of the incommensurate modulation of the fine structure tensor (D and E). The plane wave modulation model is a good approximation in the temperature range from 220°C to 120°C. The critical index β for the amplitude of the modulation wave is 0.34±0.02 in the temperature range. Below 120°C, the soliton model is a good description for the modulation wave.