Raman scattering in Zn$_{1-x}$Fe$_{x}$Te, a van Vleck diluted magnetic semiconductor*

Zn$_{1-x}$Fe$_{x}$Te, a zinc blende II-VI diluted magnetic semiconductor(DMSs), exhibits van Vleck paramagnetism, thanks to the electronic level structure of Fe$^{2+}$ with T$_{d}$ site symmetry, Subjected to crystal field and spin-orbit coupling, the lowest level of its ground state multiplet has a $\Gamma _{1}$ non-magnetic level, with a $\Gamma _{4}$ magnetic level just above it. This level ordering leads to its van Vleck paramagnetism. The Raman spectra of this DMS display the $\Gamma _{1}\to \Gamma _{4 }$electronic transition($\Gamma ^{\ast })$ whose Zeeman splittings are interpreted in terms of symmetry considerations and numerical calculations. The magnetic field and the temperature dependence of the spin-flip Raman line of the donor-bound electron in Zn$_{1-x}$Fe$_{x}$Te exhibit characteristics typical of van Vleck paramagnetism and, in combination with magnetization measurements, yield the s-d exchange constant $\alpha $N$_{0}$=236.9$\pm $9 meV. The Raman spectra also show $\Gamma ^{\ast }$ in combination with LO phonons which exhibit an intermediate mode behavior.