Reentrant charge-ordering transition and phase separation in the layered perovskite La2-2xSr1+2xMn2O7

Reentrant charge ordering (CO) has been evident as a systematic nature in the bilayered manganites La2-2xSr1+2xMn2O7 (0.45 less than or equal to x less than or equal to 0.60) at low temperatures. Measurements of physical proper-ties reveal that the reentrant CO melting (RCOM) is essentially derived by a phase competition between CO and ferromagnetism. Phase separation, along with the RCOM, has been directly observed by means of low-temperature transmission-electron microscopy.