Spectroscopic ellipsometry study of optical anisotropy inGd5Si2Ge2and comparison with reflectance difference spectra

Abstract

The complex dielectric functions of single crystals of Gd 5 Si 2 Ge 2 were obtained using spectroscopic ellipsometry ͑SE͒ in the photon energy range of 1.5-5.0 eV at room temperature. Reflectance difference ͑RD͒ spectra for the a-b and b-c planes of single crystals of Gd 5 Si 2 Ge 2 were derived from these dielectric functions and compared to those obtained from reflectance difference spectroscopy ͑RDS͒ at near-normal incidence. The two experimental RD spectra from SE and RDS agreed well. The in-plane optical anisotropy of the sample is mainly due to intrinsic bulk properties because of its larger magnitude ͑4 ϫ 10 −2 ͒ compared to surface-induced optical anisotropies, with a magnitude of only about 10 −3 for a typical cubic material.

R5T4 Compounds

“…Later it was found that the silicide adopts the Gd 5 Si 4 -type structure. The variation of T C with pressure for Dy 5 Si 4 was found to be linear with dT C /dP equal to 3.0 K/GPa (Parviainen, 1980). The variation of T C with pressure for Dy 5 Si 4 was found to be linear with dT C /dP equal to 3.0 K/GPa (Parviainen, 1980).…”

“…Formation of the Ho 5 Si 4 compound was investigated by Eremenko et al (1995), and it was reported that it forms by peritectic reaction L þ Ho 5 Si 3 ! The variation of T C with pressure for Ho 5 Si 4 was found to be linear with dT C /dP equal to 1.8 K/GPa (Parviainen, 1980). They reported a canted alignment of magnetic moments and a presence of two coexisting magnetic structures.…”

“…The Gd core levels show similarity with Gd metallic compounds and differences from Gd ionic compounds. Park et al (2006) obtained complex dielectric functions of Gd 5 Si 2 Ge 2 single crystal using spectroscopic ellipsometry in nearly same photon energy range (1.5-5.0 eV). A comparison of the spectra measured above and below the structural transition did not show any clear changes in the 0 to 4 eV binding energy region.…”