Competing two-phase coexistence in doped manganites: Direct observations by in situ Lorentz electron microscopy

J. Q. He, V. V. Volkov, T. Asaka, S. Chaudhuri, R. C. Budhani, and Y. Zhu
Phys. Rev. B 82, 224404 – Published 3 December 2010

Abstract

We examined thin epitaxial films La5/8yPryCa3/8MnO3 (LPCMO:y=0.2750.3) in situ by Lorentz transmission electron microscopy (TEM) and other microscopy methods. Clear evidence was obtained for the competing two-phase coexistence of antiferromagnetic charge-ordered (CO) and ferromagnetic (FM) phases that exhibit mesoscale phase separation below the metal-to-insulator transition (MIT) at 164K. In addition, we observed some regions of mixed CO- and FM-domain contrast attributed earlier to formation of the new CO-FM phase. Using in situ heating/cooling TEM experiments, we interpret this effect as the interfacial wetting phenomenon inherent to the first-order CO-FM phase transition, rather than to the formation of new CO-FM phase. It is evidenced by the partial magnetic melting of CO phase at interfaces with the FM phase, thereby creating charge-disordered spin-glass metastates. For coexisting CO- and FM-domain configurations, we directly refined the relationship between charge-orbital and spin-ordering vectors, consistent with FM moments pinned by (101)-crystal twins in LPCMO films. We also discuss the striking linear dependence observed below MIT for the log-resistance behavior and the CO fraction in LPCMO directly measured by TEM. Such linear dependence does not follow typical percolation equations, suggesting that percolation model needs further revisions for transport description of manganites.

    • Received 31 July 2010

    DOI:https://doi.org/10.1103/PhysRevB.82.224404

    ©2010 American Physical Society

    Authors & Affiliations

    J. Q. He1,*,†, V. V. Volkov1,*,‡, T. Asaka1,§, S. Chaudhuri2,∥, R. C. Budhani2,3, and Y. Zhu1

    • 1Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
    • 2Condensed Matter-Low Dimensional Systems Laboratory, Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
    • 3National Physical Laboratory, New Delhi 110012, India

    • *Corresponding authors.
    • Present address: Department of Chemistry, Northwestern University, Evanston, Illinois 60208; jiaqing-he@northwestern.edu
    • volkov@bnl.gov
    • §Present address: Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokisho-cho, Showa-ku, Nagoya 466-8555, Japan.
    • Present address: Nanoscience Center, Department of Physics, University of Jyväskylä, P.O. Box 35, FIN-40014 University of Jyväskylä, Finland.

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    Issue

    Vol. 82, Iss. 22 — 1 December 2010

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