Ordered states in itinerant magnets may be related to magnetic moments displaying some weak local moment characteristics, as in intermetallic compounds hosting transition metal coordination complexes. In this paper, we report on the Fe K-edge X-ray absorption spectroscopy (XAS) of the itinerant magnets RFe4Sb12 (R =Na, K, Ca, Sr, Ba), aiming at exploring the electronic and structural properties of the octahedral building block formed by Fe and the Sb ligands. We find evidence for strong hybridization between the Fe 3d and Sb 5p states at the Fermi level, giving experimental support to previous electronic structure calculations of the RFe4Sb12 skutterudites. The electronic states derived from Fe 3d Sb 5p mixing are shown to be either more occupied and/or less localized in the cases of the magnetically ordered systems, for which R = Na or K, connecting the local Fe electronic structure to the itinerant magnetic properties. Moreover, the analysis of the extended region of the XAS spectra (EXAFS) suggests that bond disorder may be a more relevant parameter to explain the suppression of the ferromagnetic ordered state in CaFe4Sb12 than the decrease of the density of states.
Long-distance correlations (LDCs) of plasma potential fluctuations in the plasma edge have been investigated in the TCABR tokamak in the regime of edge biasing H-mode using an array of multi-pin Langmuir probes. This activity was carried out as part of the scientific programme of the 4th IAEA Joint Experiment (2009). The experimental data confirm the effect of amplification of LDCs in potential fluctuations during biasing recently observed in stellarators and tokamaks. For long toroidal distances between probes, the cross-spectrum is concentrated at low frequencies f < 60 kHz with peaks at f < 5 kHz, f = 13–15 kHz and f ∼ 40 kHz and low wave numbers with a maximum at k = 0. The effects of MHD activity on the LDCs in potential fluctuation are investigated.
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