Negative thermal expansion of the Ho2AlFe14Mn2 compound

The structure properties of Ho2AlFe16-xMnx compounds have been investigated by means of x-ray diffraction and magnetic measurements. The Ho2AlFe16-xMnx compounds have a hexagonal Th2Ni17-type structure. Their unit-cell volumes increase nonlinear with increasing x. This implies there is a positive spontaneous volume magnetostriction in the magnetic state of these compounds. x-ray diffraction of the Ho2AlFe14Mn2 compound from 160 to 285 K shows that there appears a negative coefficient of thermal expansion from 220 to 270K and the average thermal expansion is -14×10-4·K-1.