Microwave imaging of charge-ordered phase coexistence in a layered manganite

Microwave impedance microscopy has been used to probe the co-existence of two charge- and orbital-ordered phases with slightly different in-plane conductivity in the layered manganite Pr(Sr$_{\mathrm{0.1}}$Ca$_{\mathrm{0.9}})$Mn$_{\mathrm{2}}$O$_{\mathrm{7}}$. Hysteretic, spatially inhomogeneous transitions between 1) the two charge-ordered phases and 2) the charge-ordered and disordered phases are observed, in which the transition temperature is affected by local strain induced by the presence of microscopic structural twin domains. In addition, conductivity contrast features are observed in the higher temperature, anti-ferroelectric charge ordered phase, which may represent anti-ferroelectric domain walls.