Monoclinic microdomains and clustering in the colossal magnetoresistance manganites ${\mathrm{Pr}}_{0.7}$${\mathrm{Ca}}_{0.25}$${\mathrm{Sr}}_{0.05}$Mn${\mathrm{O}}_3$ and ${\mathrm{Pr}}_{0.75}$${\mathrm{Sr}}_{0.25}$Mn${\mathrm{O}}_3$

A detailed high-resolution microscopy investigation of two praseodymium manganites, ${\mathrm{Pr}}_{0.7}$ ${\mathrm{Ca}}_{0.25}$ ${\mathrm{Sr}}_{0.05}$Mn${\mathrm{O}}_3$ and ${\mathrm{Pr}}_{0.75}$ ${\mathrm{Sr}}_{0.25}$Mn${\mathrm{O}}_3$ which exhibit a resistance ratio of 2.5×${10}^5$ at 88 K and of 7 at 210 K, respectively, is reported. Existence of monoclinic domains in the orthorhombic GdFe${\mathrm{O}}_3$-type matrix and ${\left(A^{\mathrm{II}}{\mathrm{Mn}}^{\mathrm{IV}}{\mathrm{O}}_3\right)}_n$ clusters corresponding to a modification of the geometry of the Mn${\mathrm{O}}_6$ octahedra has been observed; models are proposed which illustrate the high flexibility of the [Mn${\mathrm{O}}_2$] layers.