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Spin-state polarons in lightly-hole-doped LaCoO3
A Podlesnyak1, M Russina, A Furrer
1Hahn-Meitner-Institut, Glienicker Strasse 100, Berlin 14109, Germany. podlesnyakaa@ornl.gov
Physical Review Letters
|December 31, 2008
Summary
Strong magnetic signals in lightly doped La1-xSrxCoO3 originate from spin-state polarons, confirmed by inelastic neutron scattering (INS), electron spin resonance (ESR), and nuclear magnetic resonance (NMR) studies.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Magnetism
Background:
- La1-xSrxCoO3 exhibits complex magnetic properties upon hole doping.
- Understanding the origin of magnetic signals is crucial for materials applications.
Purpose of the Study:
- To elucidate the source of intense magnetic signals in lightly hole-doped La1-xSrxCoO3 (x ≈ 0.002).
- To characterize the magnetic structures and dynamics at low temperatures.
Main Methods:
- Inelastic neutron scattering (INS) to probe magnetic excitations.
- Electron spin resonance (ESR) to investigate magnetic centers.
- Nuclear magnetic resonance (NMR) to study local magnetic environments.
Main Results:
- INS and ESR spectra revealed intense excitations with large effective g factors (≈10-18).
- NMR data indicated the formation of extended magnetic clusters.
- INS intensity analysis suggests the formation of octahedrally shaped spin-state polarons (seven Co ions).
Conclusions:
- The observed magnetic anomalies are attributed to the formation of spin-state polarons.
- Two distinct magnetic regimes were identified: spin-polaron dominated (T<35 K) and thermally activated Co3+ ions (T>35 K).
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