Magnetic properties of layered III-VI Diluted Magnetic Semiconductors (DMS)

The new class of quasi-two-dimensional III-VI Diluted Magnetic Semiconductors (DMS) exhibits a rich collection of magnetic behavior. The Ga$_{1-x}$Mn$_{x}$S system exhibits a 3-D spin-glass transition, which was unexpected given its four atom thick two dimensional structure. The best scaling fit was found for critical exponents ($\gamma $ $=$ 4.0, $\beta =$ 0.8, and $\delta =$ 5.5) similar to the three dimensional Zn$_{1-x}$Mn$_{x}$Te system. Ga$_{1-x}$Fe$_{x}$Se exhibits a prominent magnetic anisotropy over the temperature range from 10 to 400 K. Theoretical models for In$_{1-x}$Mn$_{x}$Se, In$_{1-x}$Mn$_{x}$S, and Ga$_{1-x}$Mn$_{x}$S provide good agreement with experimental results over a wide range of temperatures and fields. The mechanism behind an unusually large thermal hysteresis ($\Delta T$~$\approx $~200~K) in In$_{1-x}$Mn$_{x}$Se, which extends up to room temperature, is not completely understood at this time. Typically, thermal hysteresis in most materials has a $\Delta T$~$\approx $~20~K occurring well below room temperature. The host III-VI semiconductors themselves are among the best non-linear optical materials.