Non-Resonant Microwave Absorption in SmFeAsO 0.80 F 0.20: Line Shape and Structure Evolution with Temperature

Abstract

‘Non-resonant Microwave Absorption’ (NRMA) or the ‘Low field microwave absorption’ (LFMA) measurements on high-quality polycrystalline SmFeAsO0.80F0.20 superconducting sample were carried as functions of temperature and microwave power. The LFMA line shape is complex with two peaks namely; broad peak 1 and narrow peak 2 akin to one reported in SmFeAsO0.88F0.12 as reported by Onyancha et al (Supercond. Nov. Magn. 28, 2927–2934, 2015). This unquestionably illustrates that these peaks are a common feature in F-doped SmFeAsO. The LFMA signal as a function of temperature reveals that T c − T ∗ = 1K in SmFeAsO0.80F0.20 compared to 4 K in SmFeAsO0.88F0.12 (T ∗ is the characteristic temperature at which the narrow peak appears as we cool down the sample below T c); hence inferring that the narrow peak is fluorine doping dependent. Furthermore, LFMA signal evolution with microwave power does not show phase reversal (anomalous absorption) at 2.227 mW which is a stark contrast to what was observed in SmFeAsO0.88F0.12 as reported by Onyancha et al (Physica C: Supercond. Appl. 533:49–52, 2017). The absence of phase reversal within measured microwave power indicates presence of hysteretic Josephson junction. These findings establish few non-superconducting inclusions in SmFeAsO0.80F0.20 system.