Metal-Insulator Transition in Semimagnetic Semiconductors

A rare insulator-to-metal transition on increasing magnetic field has been observed in $n-{\mathrm{Cd}}_{0.95}{\mathrm{Mn}}_{0.05}\mathrm{Se}$ and $p-{\mathrm{Hg}}_{0.915}{\mathrm{Mn}}_{0.085}\mathrm{Te}$. The two systems belong to a new universality class due to a giant spin-splitting effect. The transition is shown to be driven by the electron-electron interactions and the newly predicted critical behavior of the conductivity is confirmed.