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Electroresistance and electronic phase separation in mixed-valent manganites
T Wu1, S B Ogale, J E Garrison
1Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA. tomwu@squid.umd.edu
Physical Review Letters
|June 21, 2001
Summary
Colossal magnetoresistance (CMR) manganites show significant electroresistance (ER) when subjected to electric fields using ferroelectric gates. This sensitivity, particularly in La(0.7)Ca(0.3)MnO(3), supports a percolative phase separation model.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid State Chemistry
Background:
- Colossal magnetoresistance (CMR) materials exhibit large changes in electrical resistance under magnetic fields.
- Understanding the influence of electric fields on CMR materials is crucial for device applications.
- Manganites, particularly La(0.7)Ca(0.3)MnO(3) (LCMO), are prominent CMR materials.
Purpose of the Study:
- To investigate the electroresistance (ER) of various manganite channels under electric fields.
- To compare the ER effect with the colossal magnetoresistance (CMR) phenomenon.
- To elucidate the underlying physical mechanisms governing the observed transport properties.
Main Methods:
- Fabrication of field-effect devices using different manganite channels (LCMO, Na(0.7)Sr(0.3)MnO(3), La(0.7)Ba(0.3)MnO(3), La(0.5)Ca(0.5)MnO(3)).
- Employing ferroelectric (PbZr(0.2)Ti(0.8)O(3) - PZT) and dielectric (SrTiO(3)) gates to apply electric fields.
- Measuring electrical transport properties, including resistance and magnetoresistance, as a function of applied electric and magnetic fields.
Main Results:
- A substantial electroresistance (ER) of approximately 76% was observed in LCMO with a PZT ferroelectric gate at an electric field of 4 x 10^5 V/cm.
- The ER effect was significantly smaller (a few percent) in other manganite channels and with a dielectric gate.
- The ER and CMR effects demonstrated a complementary relationship in their behavior.
- The magnitude and systematic trends of the ER effect strongly suggest a percolative phase separation mechanism.
Conclusions:
- The study demonstrates a large ER in LCMO, highlighting its potential for electric-field-controlled electronic devices.
- The complementary nature of ER and CMR effects provides insights into the complex electronic phase behavior of manganites.
- A percolative phase separation model effectively explains the observed transport phenomena in these materials.