Neutron-diffraction study of the carrier-concentration-induced ferromagnet-to-spin-glass transition in the diluted magnetic semiconductor Sn1-xMnxTe

In the diluted magnetic semiconductor Sn1-xMnxTe the charge-carrier concentration p is of crucial importance for the low-temperature magnetic behavior. By means of neutron-diffraction experiments, in combination with ac-susceptibility, magnetization, and specific-heat data, we show that for x=0.04 the long-range-ordered ferromagnetic state observed for p=7×1020 cm-3 gradually evolves into a spin-glass state with increasing carrier concentration. In a crystal with p=11×1020 cm-3 initially a transition to a restricted-ranged ferromagnetic order occurs when the temperature is lowered in zero field, followed by a transition to a reentrant spin-glass phase. By the application of a small magnetic field (5.0 mT) the reentrant spin-glass transition is suppressed. In a p=23×1020 cm-3 crystal a spin-glass phase is entered directly from the paramagnetic regime. The neutron-diffraction results indicate the presence of short-range ferromagnetic fluctuations in this sample. The results are discussed in the context of a Ruderman-Kittel-Kasuya- Yosida model. A three-dimensional (T,x,p) magnetic phase diagram is presented.