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Observation of a Structure and Line Shape Evolution of Non-resonant Microwave Absorption in a SmFeAs(O, F) Polycrystalline Iron Pnictide Superconductor

“…Srinivasu [33] argued that the peak appears as a result of induced phase coherence by microwave power and this coherence is later destroyed by the applied magnetic field. This possibility cannot explain our findings as measurements were done with varying temperature and the peak registered at all measured temperatures below 39 K. This scenario is different from the reports of Srinivasu et al [32] and Rastogi et al [41] where the broad peak appears within a temperature window of 2 − 3 K. Rastogi et al [41] associated this peak to Josephson coupling between the CuO 2 planes. In as much as we may be drawn to associate our findings to Josephson coupling, a transition from Abrikosov vortices to Josephson vortices has been observed at a temperature T * ∼ 41−42 K in SmFeAs(O, F) single crystals [49].…”

“…Furthermore, an NRMA signal has shown very interesting and complex features in high-temperature superconductors where several models have been invoked to discern them. These features include; paramagnetic Meissner effect [24,25], the anomalous absorption which depends on temperature [26] and rf field [27], the anomalous hysteresis [28], magnetic shielding effect [29], surface barrier effect [30], spin glassy effect [31], second and third peaks [32,33], oxygen deficiency [34], among many more. It has been established that an NRMA signal depends strongly on the form of the sample.…”

“…In the Bi2212 superconductor, 'second peak' and 'third peak' as often referred to have been observed to depend on temperature, microwave power and mutual orientations of the applied DC magnetic field [32,33,41,42]. Srinivasu [33] argued that the peak appears as a result of induced phase coherence by microwave power and this coherence is later destroyed by the applied magnetic field.…”