Carrier-concentration–induced ferromagnetism in PbSnMnTe

The influence of charge-carrier concentration on the magnetic properties of the semimagnetic semiconductor [(PbTe${)}_{1\mathrm{-}\mathrm{x}}$(SnTe${)}_{\mathrm{x}}$${]}_{1\mathrm{-}\mathrm{y}}$[MnTe] ${}_{\mathrm{y}}{}^{}{}_{}{}^{}$ (x=0.72, y=0.03) is reported. Magnetization, magnetic susceptibility, and specific heat have been measured. For carrier concentrations below p=3×${10}^{20}$ ${\mathrm{cm}}^{\mathrm{-}3}$ the alloy is paramagnetic. For p≥3×${10}^{20}$ ${\mathrm{cm}}^{\mathrm{-}3}$ an abrupt transition to a ferromagnetic phase is observed at helium temperatures. The ferromagnetic transition temperature increases with increasing p. This is the first demonstration of the effect of carrier concentration on the magnetic properties of semimagnetic semiconductors.