Incommensurate Phase in γ-Irradiated RbH₃(SeO₃)₂ and RbD₃(SeO₃)₂

Abstract

ESR spectra and dielectric constant of γ-irradiated RbH₃(SeO₃)₂ and RbD₃(SeO₃)₂ were measured simultaneously around the phase transition temperature (T_C). It has been confirmed that in these substances with the doze of about 5 Mard, an incommensurate phase appears in the temperature range of about 4∼6 K above T_C and the range broadens slightly with the increase of doze. From the analysis of temperature dependence of A tensor for SeO₂⁻ radical, it is clarified that SeO₃(II) in RbD₃(SeO₃)₂ rotates in a quite similar way with that in RbH₃(SeO₃)₂ below T_C. It was found for the first time that in RbD₃(SeO₃)₂ the dielectric constant peak along the a-axis at T_C is much larger than that along the b-axis. On these results some discussion is presented.