The temperature dependence of the electrical conductivity of composites based on magnetic particles and bentonite has been systematically investigated. The results indicate that the activation energy of charge carriers is strongly dependent on the particle sizes of the composites based on bentonite and magnetic particles. That behavior is attributed to quantum size effects within the particles. Furthermore, the influence of the magnetic particle size on the magnitude of magnetoresistance and the value of magnetic permeability in the studied samples has been established.
Imanova et al. (Sun,) studied this question.