Gd3+ electron spin resonance spectroscopy on LaO1 − xFxFeAs superconductors

We report an electron spin resonance (ESR) spectroscopy study on polycrystalline samples of the LaO 1 − x F x FeAs ( x = 0 and 0.1) compound with small levels of Gd doping (2% and 5%). The Gd ESR signal is found to be sensitive to the magnetic phase transition from the paramagnetic to the spin densi...

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Bibliographic Details
Published in:Journal of experimental and theoretical physics 2012-04, Vol.114 (4), p.662-670
Main Authors: Alfonsov, A., Murányi, F., Leps, N., Klingeler, R., Kondrat, A., Hess, C., Wurmehl, S., Köfiler, A., Behr, G., Kataev, V., Büchner, B.
Format: Article
Language:English
Subjects:
Classical and Quantum Gravitation
Disorder
Elementary Particles
Order
Particle and Nuclear Physics
Phase Transition in Condensed System
Physics
Physics and Astronomy
Quantum Field Theory
Relativity Theory
Solid State Physics
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Summary:We report an electron spin resonance (ESR) spectroscopy study on polycrystalline samples of the LaO 1 − x F x FeAs ( x = 0 and 0.1) compound with small levels of Gd doping (2% and 5%). The Gd ESR signal is found to be sensitive to the magnetic phase transition from the paramagnetic to the spin density wave (SDW) state occurring in the parent LaO 1 − x F x FeAs compounds at T SDW ∼ 130 K. Interestingly, the analysis of the low-temperature ESR spectra of the c -axis oriented Gd 1 − y La y OFeAs samples gives evidence for the magnetically nonequivalent Gd sites and also for sites having a different local charge environment. The analysis of the temperature dependence of the ESR linewidths gives evidence for a coupling of the localized 4 f electrons of Gd to the conduction electrons in the FeAs layers. The ESR data reveal that the fluorine substitution, which provides electron doping, suppresses the SDW order and enhances the density of states in the electronic bands stemming from the xz and yz orbital states of Fe to which the 4 f electrons are most strongly coupled.
ISSN:1063-7761
1090-6509
DOI:10.1134/S1063776112030120