Temperature evolution of the local atomic structure in oxygen isotope substituted Pr 0.525 La 0.175 Ca 0.3 MnO 3

The local atomic structure of two oxygen isotope substituted samples of Pr0.525La0.175Ca0.3MnO3 with 16O and 18O has been studied as a function of temperature using the pair-distribution function (PDF) obtained from pulsed neutron diffraction. The sample containing 16O undergoes an insulator–metal (IM) transition below 100 K while the sample substituted with 18O remains insulating at all temperatures. We find from the PDF that the shape of the MnO6 octahedra changes from being elongated, due to a Jahn–Teller distortion, to a more regular shape below the IM transition in the 16O sample, whereas the 18O sample remains distorted at all temperatures.