Sjl. Billinge et al., DIRECT OBSERVATION OF LATTICE POLARON FORMATION IN THE LOCAL-STRUCTURE OF LA1-XCAXMNO3, Physical review letters, 77(4), 1996, pp. 715-718
The local atomic structure of La1-xCaxMnO3 (x = 0.12, 0.21, and 0.25)
has been studied using pair-distribution-function analysis of neutron
powder-diffraction data. A change is seen in the local structure which
can be correlated with the metal-insulator transition in the x = 0.21
and 0.25 samples. This local structural change is modeled as an isotr
opic collapse of oxygen towards Mn of magnitude delta = 0.12 Angstrom
occurring on one in four Mn sites. We argue that this is the direct ob
servation of lattice polaron formation, associated with the metal-insu
lator transition in these materials.