Optical imaging of multiphase coexistence inNd1∕2Sr1∕2MnO3

Abstract

We report on the imaging of the coexistence of the $CE$-type charge-ordered insulator (COI) phase and the ferromagnetic metal (FMM) phase of ${\mathrm{Nd}}_{1∕2}{\mathrm{Sr}}_{1∕2}\mathrm{Mn}{\mathrm{O}}_{3}$ by means of polarized optical microscopy over a range in temperature of several degrees. Consistent with the different $\mathrm{Mn}\ensuremath{-}\mathrm{O}$ bond lengths along the $c$ axis and in the $ab$ plane, optical anisotropy is observed in the COI, FMM, and paramagnetic insulator phases. Upon cooling, accommodation strain leads to the rapid formation of martensiticlike COI variants within the FMM phase. Upon warming, the FMM phase is observed to nucleate slowly on COI variant boundaries where the magnitude of the strain is locally maximized. Consistent with the presence of strain, COI twin boundaries sometimes demonstrate optical anisotropy and can act as sites for FMM phase nucleation.