Abstract
Neutron scattering has been used to investigate the evolution of the
long- and short-range charge-ordered (CO), ferromagnetic
(FM), and antiferromagnetic (AF) correlations in single crystals
of $\rm Pr_{1-x}Ca_{x}MnO_3$ ($x$ = 0.3, 0.35 and 0.4). These correlations are a
ssociated with the existence of spin clusters with populations that drastically depend on the doping ($x$) and temperature. Concentrated spin clusters coexist with long-range canted AF order in a wide temperature range for $x$ = 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 $\sim$ 35 K where spin clusters form. These results provide
direct evidence of magnetic phase separation and indicate that there
is a critical doping $x_{c}$ (close to $x$ = 0.35) that divides the
phase-separated site-centered from the homogeneous bond-centered
or charge-disproportionated CO ground state.
