Charge delocalization and structural response in layered La(sub 1.2)Sr(sub 1.8)Mn(sub 2)O(sub 7): Enhanced Jahn-Teller distortion in the metallic regime

摘要

Temperature dependent neutron diffraction studies on melt-grown crystals of the layered compound La(sub 1.2)Sr(sub 1.8)Mn(sub 2)O(sub 7) reveal a dramatic structural response to the onset of ferromagnetism and the coincident insulator-metal transition. Unlike the related manganite perovskites, whose Jahn-Teller distorted octahedra become more regular at temperatures below the metal-insulator transition, the MnO(sub 6) octahedra of this layered material are more severely distorted when the charge is itinerant than when it is localized.