Infrared Active Phonons and Optical Band Gap in Multiferroic GdMnO₃Studied by Infrared and UV-Visible Spectroscopy

Abstract

Optical properties of multiferroic GdMnO3 synthesized by sol-gel method have been investigated by measuring the infrared reflectivity and UV-visible absorption spectra. The infrared reflectivity spectrum of polycrystalline GdMnO3 in the frequency range 30-7500 cm −1 at room temperature contains several phonon modes. The resonant frequency of observed infrared active phonon modes is found comparable with theoretically predicted results. Mean Born effective charges are calculated and discussed in view of the origin of ferroelectricity in GdMnO3. Three strong absorption peaks observed in the UV-visible spectrum are attributed to the Mn (3d)-electron transitions. The optical band gap ≈ 1.2 eV is estimated from UV-visible absorption spectrum using Tauc's relation. GdMnO3 seems to behave like an indirect gap semiconductor.

Site-substitution in GdMnO3 : effects on structural, electronic and magnetic properties

“…From the partial density of state (Fig. 6(b)), a band gap of 1.2 eV is obtained between these JT-split Mn e g ↑ bands, which is in agreement with the calculated indirect band gap from absorption study of polycrystalline GdMnO 3 48 . The second peak of XAS spectrum around 529 eV is associated with t 2g ↓ and e g ↓ states, with a small contribution from e g ↓ around 530.5 eV.…”

Lattice Dynamics of Gd1−xYxMn2O5 Investigated by Infrared Spectroscopy

“…IR reflectivity has been measured in the frequency range of far (30-680 cm −1 ) and mid (550-7500 cm −1 ) infrared regions at room temperature under vacuum purge. Detail of measurements can be seen elsewhere [22]. similar phase sequences for all concentration .…”

Effect of Re and Tm-site on morphology structure and optical band gap of ReTmO3 (Re: La, Ce, Nd, Gd, Dy, Y and Tm: Fe, Cr) prepared by sol-gel method

“…The rare earth manganites ReMnO 3 exhibit semiconducting behavior at room temperature, as well as strong magnetoelectric coupling below Neel transition temperature (T N ). Different compounds of the ReMnO 3 have been synthesized by sol-gel method resulting in remarkable physical properties [8][9][10][11][12][13]. Nanoparticles of rare earth cobaltate perovskite ReCoO 3 were also synthesized by many researchers with sol-gel method and these compounds also exhibiting orthorhombic crystal symmetry with some interesting physical properties [14][15][16][17][18].…”