We have studied electronic and magnetic properties of the K 0.8Fe 1.6Se 2 superconductor by x-ray absorption and emission spectroscopy. Detailed temperature-dependent measurements along with a direct comparison with the binary FeSe system have revealed coexisting electronic phases: a majority phase with a high-spin 3 +Fe state and a minority phase with an intermediate-spin 2 +Fe state. The effect of high-temperature annealing suggests that the compressed phase with a lower-spin 2 +Fe state is directly related to the high-T c superconductivity in the title system. The results clearly underline the glassy nature of superconductivity in the electronically inhomogeneous K 0.8Fe 1.6Se 2, similar to the superconductivity in granular phases.
|Physical Review B - Condensed Matter and Materials Physics
|Published - 2012 6月 7
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