Paramagnetic collective electronic mode and low temperature hybrid modes in the far infrared dynamics of orthorhombic NdMnO₃

Abstract

We report on far-and mid-infrared reflectivity of NdMnO 3 from 4 K to 300K. Two main features are distinguished in the infrared spectra

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

“…For instance, the mode at 379 cm −1 could be associated with B 2u mode expected at 388 cm −1 or with B 1u mode at 367 cm −1 . Nevertheless, the ω TO of the observed phonon modes are found in good agreement with those reported for the materials with approxilar crystal structure like polycrystalline NdMnO 3 [16], LaMnO 3 [17] and single crystal GdMnO 3 polarized along a-axis [13], as summarized in Table III. As for the microscopic motion of the phonon modes is concerned, the phonon modes at 85, 116, 169, 187, and 242 cm −1 involve the motion of Gd atoms relative to MnO 6 octahedra. The Gd atoms, being heavier in the GdMnO 3 system, vibrate at low frequency.…”

“…It was also observed that the spectral signature of EuMnO 3 and GdMnO 3 is very approxilar and overall spectra do not change with temperature. Moreover, temperature dependent far-infrared reflectivity of polycrystalline NdMnO 3 have been investigated [16]. It was observed that no new phonon has been detected, so the number of modes remains unchanged in the whole low temperature range.…”

Phonons and hybrid modes in the high and low temperature far infrared dynamics of hexagonal TmMnO3

“…8 (a)) where, although not having substructure, it is also associated with zone center magnons. [37] The TA gap opening is symmetry dependent on spin and phonon dispersions and only when there is band crossing as in YMnO 3 [17] Our results presents another view of a second order transition in strongly correlated oxides for which the long-range macroscopic view given by Xray patterns, and described by a lattice space group, is not required to change.…”

“…7, appears as a room temperature smooth strong tail below 100 cm -1 . [37,38] We found that on cooling the profile change as a consequence of gradually localizing electrons inducing long-range magnetic order. The net electric Peaking at 26 cm -1 the band at lower frequency is Rare Earth dependent.…”

“…The net electric Peaking at 26 cm -1 the band at lower frequency is Rare Earth dependent. [42,37] (Fig. 8) Being sharp and well defined we simply assign peak positions based on the maximum in the spectra.…”