  The phase diagram of Pr0.65(CaySr1-y)0.35MnO3, 0.6 <= y <= 0.8, has been
determined by neutron diffraction, magnetization and electrical conductivity
measurements in order to investigate the nature of the transition between
ferromagnetic metallic and charge-ordered insulating states near y=0.75. Two
possible scenarios for this transition have been proposed: a "quantum critical
point"-like feature, near which an associated charge-disordered paramagnetic
phase is present, or a phase coexistence region. We demonstrate that the latter
case is true, phase segregation occurring on a mesoscopic/macroscopic
length-scale (several hundred Angstroms to several microns). Our results show
that no significant amount of the charge-disordered paramagnetic phase is
present at low temperatures. Our data also indicate that the charge-ordered
insulator to ferromagnetic metal phase boundary is temperature as well as
composition-dependent.
