Observation of electronic phase separation in ${\mathrm{La}}_{0.825}{\mathrm{Sr}}_{0.175}{\mathrm{Mn}}_{1-x}{\mathrm{Cu}}_x{\mathrm{O}}_3$ perovskites

We have found electronic phase separation characteristics in Cu-doped manganese perovskite ${\mathrm{La}}_{0.825}{\mathrm{Sr}}_{0.175}{\mathrm{Mn}}_{1-x}{\mathrm{Cu}}_x{\mathrm{O}}_3\mathrm{}(x>\mathrm{}0.10\mathrm{})\mathrm{}$ by electron spin resonance (ESR) and magnetization study. An extra resonance signal observed in ESR spectra at high temperatures well above $T_c$ provides strong evidence for the electronic phase separation in these materials. Our results indicate that the background superexchange interaction, here enhanced by Cu doping, is favorable for electronic phase separation in manganites.