A transition between a ferromagnetic and a spin-glass state induced by carriers

Abstract We report on the first observation of a carrier-concentration-induced phase transition in (Pb)SnMnTe, a system dominated by RKKY exchange. The magnetic properties of Pb 1− x−y Sn y Mn x Te, 0.01 x y x were studied in magnetisation, susceptibility and specific heat experiments. We shall show that for carrier concentrations, p , between 3×10 20 and 10 21 cm −3 a ferromagnetic state occurs, while for p above 10 21 cm −3 the system turns into a spin-glass-like state. This phase transition can be identified with the transition speculated about in RKKY-driven systems. The phase diagram in x−p parameter space will be derived using a simple geometrical argument, and in terms of a Sherrington-Kirkpatrick model calculation for spin glasses.