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Nonlinearity exponent of ac conductivity in disordered systems.
U N Nandi1, S Sircar, A Karmakar
1Department of Physics, Scottish Church College, Kolkata, India. un_nandi@yahoo.co.in
Summary
We studied AC conductance in iron-doped manganites, finding a universal scaling behavior across different disorder levels and temperatures. This reveals a general approach for understanding conductivity in complex materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid State Physics
Background:
- Mixed-valent polycrystalline manganite oxides exhibit complex electrical properties.
- Understanding AC conductance in disordered materials is crucial for device applications.
Purpose of the Study:
- To investigate the AC conductance of iron-doped LaMnO3 as a function of frequency, disorder, and temperature.
- To establish a general scaling formalism for AC conductivity in disordered systems.
Main Methods:
- Measured the real part of AC conductance (Σ) versus frequency (f) in LaMn(1-x)Fe(x)O(3).
- Varied quenched disorder (x) at fixed temperature and temperature (T) at fixed disorder.
- Analyzed the frequency dependence of conductance, including low-frequency plateau and high-frequency power-law increase.
Main Results:
- AC conductance remains constant at low frequencies and increases with frequency at higher frequencies.
- Data from varying disorder and temperature collapse onto a universal scaling curve.
- Characteristic frequency scales with initial conductance, revealing a universal onset exponent (x(f) ≈ 1).
Conclusions:
- A general scaling formalism exists for AC conductivity in disordered systems like manganites.
- The universal onset exponent suggests a consistent mechanism governing conductivity changes.
- Findings have implications for understanding electrical transport in other disordered materials.
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