College Park, Maryland      June 6 - 10 , 2004

T3-A3 (4:30 PM): Magnetic Field Induced Metal-Insulator Transition in Pr1-x(Ca1-ySry)xMnO3 (x = 0.45, y = 0.15)

F. Ye, J. A. Fernandez-Baca (Condensed Matter Sciences Division, Oak Ridge National Laboratory), P. Dai (Condensed Matter Sciences Division, Oak Ridge National Laboratory; Department of Physics and Astronomy, University of Tennessee), Y. Tomioka (Correlated Electron Research Center, National Institute of Advanced Industrial Science and Technology), Y. Tokura (Department of Applied Physics, University of Tokyo)

Recently, the electronic phase diagram of Pr1-x(Ca1-ySry)xMnO3 (x = 0.45) has been studied in the vicinity of the metal-insulator transition boundary. By controlling the eg electron bandwidth W, the ground state can be tuned to change from a charged-ordered (CO) and orbitally-ordered (OO) state (y 0.2) to a ferromagnetic metallic state (y > 0.25). This system has been reported to exhibit bicritical features near y = 0.25. We have used elastic and inelastic neutron scattering to study the magnetic correlations and spin dynamics of the sample near the insulator-metal boundary. The insulating CO/OO ground state of y = 0.15 can be melted by the application of external field. The evolution of the CO/OO when a magnetic field is applied will be discussed in the context of the competing interactions that may be responsible for the CMR effect.

This work was supported by the U.S. DOE under Contract No.DE-AC05-00OR22725 with UT-Batelle, LLC; and by NSF grant DMR-0139882.

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