Mössbauer Study of Superconductors LaFeO0.88F0.12As
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This study continues our investigation of high-temperature superconductors of LaFeO(1−x)FxAs type initiated in our previous paper (J. Supercond. Nov. Magnetism 27, 1825, ), where the high-temperature Kondo effect had been observed in the sample with x = 0.15. We proceed with exploring the properties of the LaFeO 0.88F0.12As sample, applying the X-ray diffraction (XRD) method, resistivity measurement, and the magnetic and Mössbauer measurements at the temperature range of 4.2-300 K. We observe the emergence of high-temperature Kondo effect at the temperatures between 30 and 50 K. At the same time, as opposed to the case x=0.15, we reveal the transformation of the high-temperature Kondo effect to the high-temperature superconductivity at the temperature near 25 K. The Mössbauer spectra of the sample obtained at different temperatures represent a single line, lying near zero relative velocity and do not exhibit any visible alterations. Concurrently, the application of an external magnetic field of 5 T to the sample at 5 K induces the emergence of a hyperfine magnetic splitting with the effective magnetic field on resonant nuclei Hef = 45.5 kOe. We suppose that the appearance of a magnetic ordering in the sample occurs due to the alignment of magnetic moments of impurities that confirms our hypothesis about a strong coupling of electron’s spins with the magnetic moments of impurities in iron-containing superconductors.
KeywordsHigh-temperature superconductivity Iron-containing superconductors Mössbauer spectroscopy
- 5.Mazin, I.I., Singh, D.J., Johannes, M.D., Du, M.H.: Phys. Rev. Lett. 101, 05700 (2008)Google Scholar