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Originally published in Science Express on 19 September 2002
Science 25 October 2002:
Vol. 298. no. 5594, pp. 805 - 807
DOI: 10.1126/science.1077346
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Reports

Direct Observation of Percolation in a Manganite Thin Film

Liuwan Zhang,1*dagger Casey Israel,1* Amlan Biswas,2ddagger R. L. Greene,2 Alex de Lozanne1§

Upon cooling, the isolated ferromagnetic domains in thin films of La0.33Pr0.34Ca0.33MnO3 start to grow and merge at the metal-insulator transition temperature TP1, leading to a steep drop in resistivity, and continue to grow far below TP1. In contrast, upon warming, the ferromagnetic domain size remains unchanged until near the transition temperature. The jump in the resistivity results from the decrease in the average magnetization. The ferromagnetic domains almost disappear at a temperature TP2 higher than TP1, showing a local magnetic hysteresis in agreement with the resistivity hysteresis. Even well above TP2, some ferromagnetic domains with higher transition temperatures are observed, indicating magnetic inhomogeneity. These results may shed more light on the origin of the magnetoresistance in these materials.

1 Department of Physics, University of Texas, Austin, TX 78712, USA.
2 Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742, USA.
*   These authors contributed equally to this work.

dagger    Permanent address: Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China.

ddagger    Present address: Department of Physics, University of Florida, Gainesville, FL 32611-8440, USA.

§   To whom correspondence should be addressed. E-mail: lozanne{at}physics.utexas.edu

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