  The short ranged magnetic correlations and dynamics of hole doped
$Pr_{1-x}Ca_{x}MnO_{3}$ (0.33 < x < 0.5) of different crystallite sizes have
been investigated using electron spin resonance spectroscopy (ESR). The major
contribution to the temperature dependence of paramagnetic line-width is
attributed to the spin-lattice relaxation dominated by thermally activated
hopping of small polarons with typical activation energy of 20-50 meV.
Irrespective of the crystallite size and dopant concentration, the transverse
spin relaxation time ($t_{2}$) follows a universal scaling behaviour of the
type $t_{2}$~($T/T_{0})^n$ in the paramagnetic regime, where $T_0$ and n are
scaling parameters. Using the temperature dependence of $t_{2}$, we construct a
phase diagram which shows that near half-doping, the magnetic correlations
associated with charge ordering not just survives even down to the crystallite
size of 22 nm, but is actually enhanced. We conclude that the eventual
suppression of charge ordering with reduction in particle size is possibly more
to do with greater influence of chemical disorder than any intrinsic effect.
