Compressibility of YMn2 Y6Mn23, YMn12 and ScMn2 studied by synchrotron powder diffraction

The compressibility of manganese compounds with different structures and co mpositions (YMn2, Y6Mn23, YMn12, Y(Mn0.8Fe0.2)(2) and ScMn2) was studied up to approximate to 40 GPa using a diamond anvil cell with synchrotron radia tion. In the case of YMn2 we observed a very large compressibility which decrease s considerably upon changing the atomic surrounding of the Mn atoms, as sho wn by the pseudobinary Y(Mn0.8Fe0.2)(2) and ScMn2. The other two Y-Mn compo unds Y6Mn23 and YMn12 also show enhanced compressibilities; however, they a re not as large as that of YMn2. Thermal expansion data, which were also included in the discussion, show th at the thermal expansion is closely related to the compressibility. The unu sually large differences in the compressibility and the thermal expansion a mong the compounds investigated have been attributed to a different 'chemic al pressure' acting on the Mn atoms, depending on the space available on th e Mn sites in the different structures.