Magnetic properties of Cr-based diluted magnetic semiconductors

We report on the magnetic properties of the Cr-based diluted magnetic semiconductors ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cr}}_{\mathit{x}}$Se and ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cr}}_{\mathit{x}}$S (x<0.01). The specific heat was measured in the temperature range 1.5<T<10 K and in magnetic fields up to 3 T, while the magnetization was measured at 2<T<40 K and B<6 T. The magnetic behavior is neither that of Brillouin paramagnets [Mn, Co diluted magnetic semiconductors (DMS’s)] nor of Van Vleck systems (Fe DMS’s). It results from a strong, static Jahn-Teller (JT) distortion for the Cr ions. A simple crystal-field model, which includes the JT effect, provides an overall description of the experimental data, but some discrepancies remain.