Raman scattering in the diluted magnetic semiconductorZn1−xFexTe: A van Vleck paramagnet

Abstract

${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}\mathrm{Te}$, a zinc blende II-VI diluted magnetic semiconductor (DMS), exhibits a temperature independent magnetization at low temperature (van Vleck paramagnetism) as a consequence of the electronic structure of ${\mathrm{Fe}}^{2+}$ in its site symmetry as an isoelectronic replacement of ${\mathrm{Zn}}^{2+}$. The lowest level of its $^{5}\ensuremath{\Gamma}_{3}$ ground state multiplet has a ${\ensuremath{\Gamma}}_{1}$ nonmagnetic level, with a ${\ensuremath{\Gamma}}_{4}$ magnetic level $2.26\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ above it. The Raman spectrum of this DMS displays the ${\ensuremath{\Gamma}}_{1}\ensuremath{\rightarrow}{\ensuremath{\Gamma}}_{4}$ electronic transition (labeled in this paper ${\ensuremath{\Gamma}}_{1\ensuremath{\rightarrow}4}$), whose Zeeman splitting is interpreted in terms of symmetry considerations and numerical calculations. The magnetic field and temperature dependence of the spin-flip Raman line $({\ensuremath{\omega}}_{\mathit{SFR}})$ of the donor-bound electron in ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}\mathrm{Te}$ exhibit characteristics typical of the van Vleck paramagnetism and, in combination with magnetization measurements, yield the $s\text{\ensuremath{-}}d$ exchange constant ${N}_{0}\ensuremath{\alpha}=239.0\ifmmode\pm\else\textpm\fi{}10\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$. The Raman spectra also show ${\ensuremath{\Gamma}}_{1\ensuremath{\rightarrow}4}$ in combination with the LO phonons of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}\mathrm{Te}$ as a ternary alloy with an intermediate mode behavior.