Properties of ceramic manganite (La$_{0.65}$Sr$_{0.35}$)$_{1-x}$Mn$_{1+x}$O$_{3\pm\Delta}$ ($x$ = 0, 0.1, 0.2) sintered at a temperature of 1500$^\circ$C

It has been shown for the first time that the structure of (La$_{0.65}$Sr$_{0.35}$)$_{1-x}$Mn$_{1+x}$O$_{3\pm\Delta}$ ($x$ = 0, 0.1, 0.2) ceramics sintered at 1500$^\circ$C substantially depends on the content of superstoichiometric Mn. It has been found that the average grain size increases from 10 to $>$ 100 $\mu$m with increasing $x$ from 0 to 0.2. It has been revealed that grains of the ceramic samples sintered from powders with excess Mn have an internal nanoscale layered structure. A correlation has been revealed between the size and structure of grains and and the magnetoresistive properties.