Methodology to Probe Disorder Contribution in Raman Linewidth via Optical Absorption Spectroscopy in Orthoferrite EuFeO3

Abstract

The individual impact of disorder on different phonon modes has been investigated for orthoferrite EuFeO3 by perceiving a correlation between temperature-dependent Raman linewidth (Δ) and Urbach energy (EU). It has been found that the plot of Δ versus EU exhibits a linear relationship, whose slope (ζ) differs for each Raman mode. Interestingly, the Raman mode exhibiting larger temperature variation in width is found to acquire a larger slope. This has been understood as eclectic contribution of disorder toward altering the mode-widths. Furthermore, a careful analysis hints that parameter ζ may contain information of overlap between discrete (phonon) and electronic continuum (∼Urbach tail) states. This may be seen as a selective impact of disorder on individual phonons in view of the electron-phonon interaction. Hence, the slope of the linear plot between Δ and EU has been realized as a parameter that may represent the individual disorder contribution to modify Raman width of each mode, and thereby ζ has been interpreted to be the disorder-coupling parameter. © 2022 American Chemical Society.