Percolative nano-sized phase separation in mix-valent manganites

Combining transport and magnetic properties measurements, we find that ferromagnetic clusters are embedded in an antiferromagnetic matrix in the mix-valent R1-xCaxMnO3 (R denotes rare-earth element, x = 0.88-1) manganites at low temperature, namely, magnetic phase separation phenomenon. In contrast to the holedoped manganites, ferromagnetic clusters in the electron-doped manganites are likely ellipsoidal-type rather than stripe-type, evidenced by modeling the low temperature electrical transport behavior. Percolative conduction transport between the ferromagnetic clusters takes place in the case of phase separation state. As the R ion content exceeds a certain level, colossal magnetoresistance is observed in a narrow range in this system. The rotation of ferromagnetic domains under magnetic field may underlie the magnetoresistance effect in the phase separation state of these electron-doped manganite systems.