Phase separation in Pr$_{0.55}$Ca$_{1.45}$MnO$_{4}$ evidenced by magnetic excitations*

At doping levels x$<$0.5, a coexistence of commensurate (CM) and incommensurate (ICM) magnetic peaks are observed in single-layered manganites Pr$_{1-x}$Ca$_{1+x}$MnO$_{4}$ with elastic neutron scattering. Temperature dependence measurements of the magnetic intensities with different energy resolutions indicate a glassy nature of the magnetic moments. The magnetic excitation measurements using inelastic neutron scattering on the x=0.45 system reveal both symmetric and asymmetric behaviors about the CM peak positions. This strongly suggests two types of magnetic excitations originated from separated phases: the CE-type magnetic phase and an additional electronic phase caused by extra electrons introduced into the CE template.