Influence of the mechanical effect and impurity doping on the endothermic effect in SmS

The effect of heat absorption has been found for powder samples of samarium sulfide (SmS) in a temperature range of 235–250 K. The comparison with a similar effect in single-crystal SmS has been performed and thermodynamic parameters of the process have been determined. It has been shown that the collective injection of electrons into the conduction band from impurity donor levels is responsible for the appearance of this effect in both cases. The shift of the endothermic peak upon powdering toward lower temperatures and an increase in the enthalpy are associated with a decrease in the characteristic size of the X-ray coherent scattering regions and, as a consequence, with an increase in the concentration of impurity donor levels.