  The crystal and magnetic structure of polycrystalline
$La{}_{0.5-x}Nd{}_{x}Ca_{0.5}MnO{}_{3}$ (0.0 \ensuremath{\le} x
\ensuremath{\le} 0.5) samples have been investigated using magnetization,
resistivity, transmission electron microscope, and neutron diffraction
techniques. The samples are isostructural and possess orthorhombic structure in
\textit{Pnma} space group. On lowering of temperature, the samples exhibit CE -
type antiferromagnetic structure coexisting with a weak ferromagnetic ordering.
The charge and orbitally ordered antiferromagnetic phase is weakened by the
growth of ferromagnetic phase. The evolution of structural distortions and
magnetic structure at low temperature as a function of Nd doping exhibit a
strong correlation with A - site disorder ($\sigma{}^{2}$).
