Correlation Between Critical Current Density and Raman Spectra of Tetragonal REBCO

The continuously increasing interest in the use of Second Generation High Temperature Superconductor (2G-HTS) over wide range of temperatures (4.2–77 K) and intermediate to very high fields (∼3 to >30 T) entails a major problem of lack of techniques capable of inspecting critical current ( I_c ) performance at the target fields and temperatures (B, T) over long lengths. The complete lack of correlation between critical current performance at (77 K, 0T) and the target (B,T) calls for alternative techniques capable of reliable performance characterization over long lengths in a time and cost effective manner. In this study, we explore the possibility of using Raman spectroscopy features to provide insight into J_c(B,T) performance of RECBO films. We present results on correlation between features of Raman spectra of tetragonal REBCO films and their in-field J_c(B,T) performance. In particular, we identify a secondary peak in the vicinity of Cu2 peak as a feature that correlates with J_c(B,T) at intermediate fields (0–4 T) and temperatures (30–77 K). The feature appears as a shoulder or asymmetry of Cu2 peak but is fitted as a separate Voigt profiled peak. The intensity of this peak, normalized to the intensity of the Cu2 peak, has a strong negative correlation with J_c(B,T) , with Pearson correlation coefficient −0.88 to −0.97.