Polarized Raman spectra of hematite and assignment of external modes

Abstract Notwithstanding the significant practical importance of hematite, α‐Fe 2 O 3 , the complete assignment and understanding of the Raman spectrum acquired on this crystalline solid are uncertain. Above all, only one of the two external E g phonons arising from the Γ point has been resolved and hence assigned. It is well known that the E g mode at 294 cm −1 has been attributed to one of the two external phonons arising from the Γ point. To this end, we have undertaken studies to examine the polarized Raman scattering on a pure single crystal to gain a better understanding and assignment of phonons arising from the Γ point in the Raman spectrum of hematite. Here, we resolve and assign the previously unidentified external E g phonon at 245 cm −1 and, additionally, confirm that the band at 294 cm −1 is an external E g phonon, in the first‐order Raman spectrum of hematite. Further, our polarized Raman spectra display interesting polarization behavior of the 2LO mode at 1320 cm −1 , where this band is only Raman active in e i || e s polarization configurations.