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Is a Griffiths phase a prerequisite for colossal magnetoresistance?
Wanjun Jiang1, XueZhi Zhou, Gwyn Williams
1Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2 Canada. jiang@physics.umanitoba.ca
Physical Review Letters
|November 13, 2007
Summary
Colossal magnetoresistance in La(1-x)Ca(x)MnO(3) single crystals is linked to a Griffiths phase in some samples. However, this phase is not essential for observing colossal magnetoresistance near optimal doping.
Area of Science:
- Condensed matter physics
- Materials science
- Magnetism
Background:
- Colossal magnetoresistance (CMR) is a phenomenon observed in certain manganese oxides.
- La(1-x)Ca(x)MnO(3) exhibits CMR, with its properties influenced by calcium doping (x).
- Understanding the underlying mechanisms of CMR is crucial for materials science applications.
Purpose of the Study:
- To investigate the magnetic and transport properties of La(1-x)Ca(x)MnO(3) single crystals.
- To determine the role of the Griffiths phase in colossal magnetoresistance.
- To compare the behavior of samples with different doping levels.
Main Methods:
- Detailed measurements of magnetic properties.
- Detailed measurements of transport behavior.
- Analysis of critical exponents and phase transitions.
Main Results:
- The x=0.21 sample showed unusual critical exponents and a Griffiths phase (lambda = 0.70+/-0.2).
- The x=0.20 sample exhibited Heisenberg model behavior without a Griffiths phase.
- Critical temperature (T(C)) for x=0.21 was 182+/-1 K.
Conclusions:
- A Griffiths phase explains the behavior of La(1-x)Ca(x)MnO(3) near optimal doping.
- The Griffiths phase is not a prerequisite for colossal magnetoresistance in this system.
- Doping concentration significantly influences the magnetic and transport properties.
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