Negative thermal expansion and magnetic properties of Y2Al3Fe14−xMnx compounds

The structure and magnetic properties of Y2Al3Fe14−xMnx (x=0–12) compounds have been investigated by means of x-ray diffraction and magnetization measurements. The Y2Al3Fe14−xMnx compounds have a hexagonal Th2Ni17-type structure. Their unit-cell volumes increase slowly with increasing x first, then increases rapidly with the further increase of x. This implies that there exists a positive spontaneous volume magnetostriction in the magnetic state of Y2Al3Fe14−xMnx compounds. X-ray diffraction of the Y2Al3Fe11Mn3 compound from 150 to 300 K shows that there appears a negative coefficient of thermal expansion, ᾱ≈−7.5×10−5/K, from 185 to 200 K. The Curie temperature and the saturation magnetization of these compounds show a rapid drop with increasing x.