Optical and electronic properties of heusler Cu2MnAl alloy with shape memory effect

A ferromagnetic Heusler Cu₂MnAl alloy with a shape memory effect has been studied in the wide spectral region of 0.25–2.80 μm (0.44–5.35 eV) at room temperature using spectral ellipsometry methods. Dispersion dependences for optical constants n(hν) and κ(hν), dielectric permeability ε(hν), and optical conductivity σ(hν), which is proportional to the interband density of electronic states, have been analyzed. Optical conductivity spectra have been calculated by mathematical modeling based on data for the electronic state densities in both subbands of electrons with spins oriented along and against the magnetization direction. A model of indirect transitions based on the Berglund–Spicer formula has been shown to describe the experimental spectrum only in general terms. The main contribution to the conductivity in the high-frequency spectral region is due to direct transitions of electrons in the vicinities of L, X, and Γ points of the Brillouin zone coupled with Cu atoms whereas low-energy anomalies in the absorption spectrum σ(hν) are caused by electrons coupled with Mn and Al atoms.