Utilizing total scattering to study the Jahn-Teller transition in La1-xCaxMnO3

Abstract

Total scattering based atomic pair distribution function (PDF) analysis, with the advent of high data throughput neutron powder diffractometers, helps understanding the nature of the Jahn-Teller (JT) phase transition in La1-xCaxMnO3 colossal magnetoresistive (CMR) manganites. The JT distortion of the MnO6 octahedra, is long-range ordered in the orthorhombic (O) phase, but disappears in the pseudo-cubic (O') phase crystallographically. An anomalous unit cell volume contraction occurs at the transition. The PDF study indicates that the distortion persists locally deep in the O' phase, contrary to the crystallographic view. Simultaneously, local structural features observed in PDF at 10.3 A, sensitive to the oxygen sublattice changes, evolve dramatically across the transition. The same effect is observed irrespective of the way the O-O' phase boundary is crossed: it is seen both in the temperature series data for x=0, and in the doping series data at 310 K and at 550 K.