  The orbital order-disorder transition temperature (T_OO) versus tolerance
factor (t) plot switches from monotonic to non-monotonic beyond a doping level
(x) ~ 10 atom% in a family of R(1-x)A(x)MnO3 systems(R = La, Pr, Nd; A = Ca,
Sr; x = 0.0-0.2). T_OO reaches maximum at a 'doping-dependent' critical
tolerance factor t_C(x) (for 0.1<x<0.2)at which the orthorhombic distortion (D)
also maximizes. Such an observation reflects influence of charge carriers on
both 'intrinsic' octahedral-site distortion and its bias on the orbital order
in doped perovskite manganites and, thus, deviation from what has been observed
in undoped RMnO3, RTiO3, and RVO3 systems where maximization of T_OO and D
takes place at a universal tolerance factor or R-site ion size.
