Metal-insulator transitions and the magnetic susceptibility in doped cuprate compounds

The results of the theoretical study of the possibility of hole carriers localization and metal-insulator transitions that occur in the temperature dependences of the magnetic susceptibility _chi(T). of doped copper-oxide (cuprate) compounds are presented. The criteria are analyzed for the metal-insulator transitions caused by a strong hole-lattice interaction and by the formation of very narrow polaron bands in these materials with decreasing the level of doping x. It has been shown that such metal-insulator transitions in doped cuprates La_2-xSr_xCuO₄ and YBa₂Cu₃O_6+x occur in the underdoped regime (i.e., when x varies from 0.04 to 0.12). The characteristic temperature dependences _chi(T) are determined in the high-Tc cuprates with different levels of doping. The obtained results are in a good agreement with the experimental data on metal-insulator transitions and the magnetic susceptibility in the high-Tc cuprates.