Features in the behavior of temperature dependences of magnetic susceptibility of crystals of Bi$_2$Te$_3$–Sb$_2$Te$_3$ solid solutions containing from 25 to 70 percent antimony telluride

Temperature dependences of the magnetic susceptibility of $p$-type crystals of Bi$_2$Te$_3$–Sb$_2$Te$_3$ solid solutions containing from 25 to 70 mol percent antimony telluride were examined in the range from 2 to 400 K. A correlation was found between the features observed in the behavior of temperature dependences of the magnetic susceptibility of crystals containing 60 and 70 mol percent Bi$_2$Te$_3$ and the ratio of the plasmon energy to the energy of the gap between the chemical potential level and the heavy hole subband. An assumption is formulated that in the case of convergence of these energies, the increasing electron–plasmon interaction affects the electron system state and, consequently, the magnitude of magnetic susceptibility.