Signature of magnetic phase separation in the ground state of Pr1-x Cax MnO3

Neutron scattering has been used to investigate the evolution of long- and short-range charge-ordered (CO), ferromagnetic, and antiferromagnetic (AF) correlations in single crystals of Pr1-x Cax MnO3. The existence and population of spin clusters as reflected by short-range correlations are found to drastically depend on the doping and temperature. Concentrated spin clusters coexist with long-range canted AF order in a wide temperature range in the x=0.3 while clusters do not appear in the x=0.4 crystal. In contrast, both CO and AF order parameters in the x=0.35 crystal show a precipitous decrease below ∼35 K where spin clusters form. These results provide direct evidence of magnetic phase separation and demonstrate a critical doping xc (close to x=0.35) that divides the inhomogeneous from homogeneous CO ground state.