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Insular superconductivity in a Co-doped iron pnictide CaFe1-xCoxAsF
S Takeshita1, R Kadono, M Hiraishi
1Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan.
Physical Review Letters
|August 8, 2009
Summary
Muon spin rotation reveals phase separation in CaFe1-xCoxAsF. Superconducting regions form as cobalt doping increases, suggesting short coherence lengths in this magnetic superconductor.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid-State Chemistry
Background:
- CaFe1-xCoxAsF exhibits complex interplay between superconductivity and magnetism.
- Understanding phase separation is crucial for optimizing material properties.
Purpose of the Study:
- To investigate the macroscopic phase separation in CaFe1-xCoxAsF.
- To elucidate the relationship between cobalt doping and the superconducting/magnetic phases.
Main Methods:
- Muon spin rotation (µSR) spectroscopy was employed.
- Measurements were performed across the phase boundaries (x=0.05-0.15).
Main Results:
- Macroscopic phase separation between superconducting and magnetic phases was confirmed.
- The magnetic phase retains a higher transition temperature (Tm>Tc).
- Cobalt doping introduces significant randomness and forms superconducting "islands" with a short coherence length.
Conclusions:
- Superconductivity in CaFe1-xCoxAsF is characterized by spatially separated superconducting and magnetic regions.
- Cobalt doping influences the volumetric fraction and spatial distribution of the superconducting phase.
- The observed phenomena are consistent with a short superconducting coherence length in the Fe2As2 layers.
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