Magnetic behavior of the semimagnetic semiconductor (${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$${)}_3$${\mathrm{As}}_2$

The magnetization, susceptibility, and specific heat of the semimagnetic semiconductor (${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$ ${)}_3$ ${\mathrm{As}}_2$ have been measured in the temperature range 0.5 K<T<300 K and in magnetic fields up to 25 T for x<18%. A transition to a spin-glass state is observed at low temperatures. The results indicate that a relatively strong antiferromagnetic (AF) nearest-neighbor interaction $J_0$ is present together with an AF long-range interaction of the type $J_1$/$R^3$ or $J_1$/$R^4$. The magnetic moment on the Mn sites turns out to be about 4.4 Bohr magnetons and no deviation from a random distribution of the magnetic ions is observed. Based on these observations we calculated the thermodynamic properties with the extended nearest-neighbor pair correlation approximation. It appears that this approximation gives a good description of $C_m$, M, and χ simultaneously with $J_0$/$k_B$=-30 K and $J_1$/$k_B$=-20/$R^4$ K (R in units of the nearest-neighbor distance). Possible application of the model to other semimagnetic semiconductors and the possible origin of the exchange mechanism in (${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$ ${)}_3$ ${\mathrm{As}}_2$ are discussed.