Ellipsometric Study of Anisotropy Permittivity of Hexagonal Manganites RMnO3 (R = Ho, Tm, Yb)

Abstract

The optical properties of single crystals of the hexagonal manganites RMnO3 (R = Ho, Tm, Yb) have been investigated by spectroscopic ellipsometry in the spectral range 0.6-5.0 eV. The measurements show a strong anisotropy of the diagonal elements of the dielectric tensor. It has been demonstrated that the optical absorption edge for the polarization Ec was determined by the intense band of O(2p)Mn (3d) transition centered near 1.6 eV, whereas this band for the polarization Ec was strongly suppressed and shifted toward higher energies by 0.15-0.20 eV. The spectral dependences of the ε1(E) and ε2(E) for HoMnO3, TmMnO3 and YbMnO3 single crystals were qualitatively similar. The broad absorption band at E<1.0 eV clearly appears at the energies below the fundamental absorption edge of all of study compounds. It is possible, the origin of the near-infrared ε2(E) absorption is associated with 4f-4f transitions of R3+ ions.