BEHAVIOR OF THE ATOMIC AND MAGNETIC-STRUCTURE OF LA0.35PR0.35CA0.30MNO3 AT A METAL-INSULATOR PHASE-TRANSITION

The evolution of the structural and magnetic properties of the CMR (co lossal-magnetoresistance) compound La0.35Pr0.35Ca0.30MnO3 as the tempe rature changes from 10 to 293 K is investigated by means of neutron di ffraction. It is shown that the changes in the transport and magnetic properties are directly related with the rearrangement of die atomic s tructure. A phase transition to the metallic state occurs together wit h simultaneous ferromagnetic ordering of the manganese moments and is accompanied by a jump in volume. The static distortions of the oxygen octahedra which are observed to occur prior to the magnetic phase tran sition and which are practically absent at room temperature and in the FM phase attest to the orbital ordering of oxygen atoms on the bonds, with freezing-in of the Jahn-Teller modes. (C) 1998 American Institut e of Physics. [S0021-3640(98)01209-2].