Relaxation between charge order and ferromagnetism in manganites: Indication of structural phase separation

We have investigated two regions of manganite phase space; one where ferromagnetic (FM), metallic and charge-ordered (CO), insulating phases become the ground and high-temperature states, respectively, and the other with the reversed order. We found that the coexistence of FM and CO phases in broad temperature ranges carl be drastically influenced by cooling rate and also aging, showing the presence of slow relaxation. Our results can be understood in terms with free energy analysis combined with long-range, anisotropic strain consideration, indicating that the coexistence of the distinct electronic phases is structural in origin.