Optical and magnetooptical properties of Heusler alloys XMnSb (X = Co, Pt)

Abstract

The ellipsometry method (with photon energies ħω= 0.1–5.0 eV) has been used to study the optical properties of the CoMnSb phase with a structure of the L21 type. Infrared-absorption features indicating the existence of a pseudogap in the density of states at the Fermi level N(E F) have been revealed. The transverse Kerr effect in CoMnSb and PtMnSb has been measured at photon energies ħω = 0.4–4.5 eV. It has been shown that the observed peaks of magnetooptical activity in CoMnSb are due to the off-diagonal component ɛ ij of the tensor of the complex dielectric constant \(\hat \varepsilon\). Spectral dependences of the magnetooptical effect δ q quadratic in magnetization M have been studied for the first time for PtMnSb for the s and p polarizations of the light wave. In the region where a giant Kerr effect (ħω ∼ 1.7 eV) is observed in PtMnSb, a sharp increase in the δ q effect has been revealed caused by the change in the diagonal component ɛ ii of the tensor] of the dielectric constant in an external magnetic field. Based on the δ q spectra for the p polarization of the light wave, additions have been calculated to the real and imaginary parts of the diagonal component of the \(\hat \varepsilon\) tensor in the magnetic field (Re(Δɛ ij ) p and (Δɛ) ij ) p , respectively). The spectrum of Im(Δe ij ) p has been analyzed in terms of the existing concepts on the electron structure of PtMnSb.