Phase separation and segregation in rare earth manganates: the experimental situation

Rare earth manganates of the general formula, Ln1−x A x MnO3 (Ln=rare earth, A=alkaline earth) exhibit phase separation due to the occurrence of tiny clusters or small nanometric regions of one type of magnetic phase in the matrix of another (e.g., ferromagnetic metallic clusters in an insulating antiferromagnetic matrix) or phase segregation due to the coexistence of large domains of two phases. The phenomenon is nearly universal in the manganates and crucially depends on the composition, temperature, external magnetic field, dopant substitution in the Mn site and related factors. Percolative transport has been considered to result from the coexistence of the ferromagnetic metallic and insulating phases, but it is necessary to ensure whether these phases form large domains or remain as clusters (<100 nm) in the relevant composition.