Session Q22: Metal-Insulator Phase Transitions II

11:15 AM–2:15 PM, Wednesday, March 23, 2011
Room: D163

Sponsoring Unit: DCMP
Chair: Cengiz Sen, University of Tennessee

Abstract ID: BAPS.2011.MAR.Q22.4

Abstract: Q22.00004 : In-situ TEM Analysis and Transport in Manganites La$_{5/8-y}$Pr$_{y}$Ca$_{3/8}$MnO$_{3}$ Exhibiting Phase Separation below Metal-Insulator Transition

11:51 AM–12:03 PM

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Authors:

  V. Volkov
    (Brookhaven National Laboratory)

  J. He
    (Brookhaven National Laboratory)

  T. Osaka
    (Brookhaven National Laboratory)

  Y. Zhu
    (Brookhaven National Laboratory)

  S. Chaudhuri
    (Indian Institute of Technology)

  R. Budhani
    (Indian Institute of Technology)

Epitaxial films of doped La$_{5/8-y}$Pr$_{y}$Ca$_{3/8}$MnO$_{3}$ (LPCMO: y = 0.275-0.375) manganites were examined by \textit{in-situ} Lorentz microscopy and other TEM methods below the metal-insulator transition point T$_{MI}\sim $164 K. Such films are known for colossal magneto-resistance effect (CMR). Clear evidences were obtained for mesoscale two-phase separation process involving antiferromagnetic charge-ordered (AFM/CO) and ferromagnetic (FM) phases, coexisting below T$_{MI}$ in LPCMO films. The first-order CO-FM phase transition is accompanied by partial magnetic melting of the CO phase at CO/FM interfaces thereby creating charge-disordered spin-glass metastates. In contrast, FM phase shows specific ``zig-zag'' magnetic domains coupled with dense (101) crystal twins. This allows refining relations for charge-orbital and spin-ordering vectors in films. Transport resistance data show that T$_{MI}$ point is decreased with Pr$_{y}$ growth in LPCMO. On cooling films below T$_{MI}$ their resistance drops by several orders in magnitude. The observed M-I transition shows striking linear relation for log-conductance curve versus FM fraction measured by TEM, which does not follow typical percolation equations, suggesting that percolation transport model in manganites needs further revisions.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.Q22.4