Methodology to Probe Disorder Contribution in Raman Linewidth via Optical Absorption Spectroscopy in Orthoferrite EuFeO<sub>3</sub>
Omkar V. Rambadey, Anil Kumar, Kailash Kumar, Vikash Mishra, Pankaj R. Sagdeo
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 (Γ) and Urbach energy (EU). It has been found that the plot of Γ versus EU exhibits a linear relationship, whose slope (ξ) 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 ξ 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 Γ and EU has been realized as a parameter that may represent the individual disorder contribution to modify Raman width of each mode, and thereby ξ has been interpreted to be the disorder-coupling parameter.