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Published Online September 19, 2002
Science DOI: 10.1126/science.1077346

Reports

Submitted on August 14, 2002
Accepted on September 9, 2002

Direct Observation of Percolation in a Manganite Thin Film

Liuwan Zhang 1, Casey Israel 2, Amlan Biswas 3, R. L. Greene 4, Alex de Lozanne 2*

1 Department of Physics, University of Texas, Austin, TX 78712, USA; Department of Physics, Tsinghua University, Beijing 100084, Peoples Republic of China.
2 Department of Physics, University of Texas, Austin, TX 78712, USA.
3 Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742, USA; Department of Physics, University of Florida, Gainesville, FL 32611-8440, USA.
4 Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742, USA.

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

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.


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