Magnetic Specific Heat Study of the Competition between Ferro- and Antiferromagnetic Spin-Spin exchange Interactions in PbSnMnTe

Magnetic contribution to the specific heat, magnetic susceptibility and Hall effect are experimentally studied in Pb$\text{}_{1-x-y}$Sn$\text{}_{y}$Mn$\text{}_{x}$Te semimagnetic semiconductors with y=0.72 and x=0.08 and with different carrier concentrations 10$\text{}^{20}$ ≤ p ≤ 10$\text{}^{21}$ cm$\text{}^{-3}$. The ferromagnetism observed in crystals with p ≥ 3×10$\text{}^{20}$ cm$\text{}^{-3}$ breaks down with a decreasing concentration of carriers due to an increasing competition between Ruderman-Kittel-Kasuya-Yoshida and superexchange interactions.