Thermal Expansion Coefficients of Manganese Fluoride

Abstract

The expansivity ($\frac{\ensuremath{\Delta}l}{{l}_{273.2}}$) and linear thermal expansion coefficient [${l}^{\ensuremath{-}1}{(\frac{\mathrm{dl}}{\mathrm{dT}})}_{p}$] have been measured for the $a$ and $c$ axes of manganese fluoride. There is a marked anomaly in the linear thermal expansion coefficients at the N\'eel temperature; the N\'eel temperature was found to be 67\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}1\ifmmode^\circ\else\textdegree\fi{}K. The anomaly has the characteristic shape associated with order-disorder transformations.