High-temperature (295 - 1000 K) Raman studies of Nd-doped bismuth ferrite epitaxial heterostructures were performed. The bands 620 cм-1 and 1260 cm-1 were observed in the high-frequency range above the first-order phonons. The band 620 cм-1 corresponds to the maximum density of states of magnon branch at the Brillouin zone boundary. The intense second-order band at about 1260 cm-1 corresponds to the density of states of two-magnon excitations. The intensity of two-magnon scattering decreases with increasing temperature, and above the Neel temperature paramagnon scattering typical for antiferromagnetics was observed.

Keywords: Raman spectroscopy, multiferroic, bismuth ferrite, heterostructure

In this paper a systematic study of individual single-walled and multi-walled carbon nanotubes was performed by Raman spectroscopy and high-resolution electron microscopy. We have presented the geometrical and electronic structure analysis on the examples of two tubes: individual single-walled and double-walled nanotubes. The role of different environmental effects and their influence on the final structure assignment are discussed. Moreover, we have shown that the Raman spectroscopy gives reliable estimations of the nanotube diameters and the conductivity. Given a non-destructible character of Raman spectroscopy, we may conclude that it is one of the most efficient methods for structure analysis of carbon nanotubes.

Keywords: Carbon nanotubes, Raman spectroscopy, electron microscopy