Comparison between the neutron central peak and the x-ray quasi-Bragg peak in pure KMnF3.

Abstract

High-resolution x-ray and neutron-scattering experiments have been performed on the same sample of ${\mathrm{KMnF}}_{3}$ in order to compare the temperature behavior of the neutron ``central peak'' and of the x-ray ``quasi-Bragg'' peak. It is found that the peak intensity of both the central and quasi-Bragg peaks evolves similarly as (T-${\mathit{T}}_{\mathit{c}}$${)}^{\mathrm{\ensuremath{-}}\ensuremath{\gamma}}$ with ${\ensuremath{\gamma}}_{\mathrm{CP}}$=1.34\ifmmode\pm\else\textpm\fi{}0.08 and ${\ensuremath{\gamma}}_{\mathrm{QBP}}$=1.26\ifmmode\pm\else\textpm\fi{}0.04. This result, together with considerations about experimental conditions, strongly suggests that the central peak and the quasi-Bragg peak are the same feature even if they are not observed in the same range of temperature.