Thermal Expansion Coefficients of Manganese Fluoride

The expansivity ($\frac{\Delta l}{l_{273.2}}$) and linear thermal expansion coefficient [$l^{-1\mathrm{}}{\left(\frac{\mathrm{dl}}{\mathrm{dT}}\right)}_p$] 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 Néel temperature; the Néel temperature was found to be 67°±1°K. The anomaly has the characteristic shape associated with order-disorder transformations.