Europhys. Lett, 47 (1), pp. 90-96 (1999)
Persistent X-ray photoconductivity and percolation of metallic clusters in charge-ordered manganites
D. Casa 1, V. Kiryukhin 1, O. A. Saleh 1, B. Keimer 2, J. P. Hill 3
Y. Tomioka 4 and Y. Tokura 5
1 Department of Physics, Princeton University, Princeton - NJ 08544, USA
2 Max-Planck-Institut für Festkörperforschung - D-70569 Stuttgart, Germany
3 Department of Physics, Brookhaven National Laboratory - Upton, NY 11973, USA
4 Joint Research Center for Atom Technology (JRCAT), Tsukuba - Ibaraki 305, Japan
5 Department of Applied Physics, University of Tokyo - Tokyo 113, Japan
(received 8 March 1999; accepted in final form 23 April 1999)
PACS. 72.40 - Photoconduction and photovoltaic
PACS. 71.30 - Metal-insulator transitions and other electronic transitions.
PACS. 72.80Ga - Transition-metal compounds.
Charge-ordered manganites of composition exhibit persistent photoconductivity upon exposure to X-rays. This is not always accompanied by a significant increase in the number of conduction electrons as predicted by conventional models of persistent photoconductivity. An analysis of the X-ray diffraction patterns and current-voltage characteristics shows that X-ray illumination results in a microscopically phase-separated state in which charge-ordered insulating regions provide barriers against charge transport between metallic clusters. The dominant effect of X-ray illumination is to enhance the electron mobility by lowering or removing these barriers. A mechanism based on magnetic degrees of freedom is proposed.
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