  The orbital effect on the anomalous magnetism and evolution of low La-doping
single crystals, La$_x$Y$_{1-x}$VO$_{3}$ (x = 0, 0.1, and 0.2), has been
investigated by applying the X-ray diffraction, specific heat, magnetization
and Raman scattering techniques. The larger nearest-neighbor (NN) exchange
interaction along c-axis stabilizes the fluctuant G-type orbital ordering
(G-OO) which favors the exotic C-type antiferromagnetic order (C-AF). It is
found that the NN exchange interaction in ab plane is anisotropy relating to
the in plane magnetic anisotropy, which becomes smaller in high La-doped
sample. Most interestingly, with increasing the La$^{3+}$ content the orbital
fluctuation and hybridization are decreased which stabilizes the C-OO phase and
destabilizes the G-OO phase. Meanwhile, the diamagnetism in the exotic C-AF
phase becomes weak and the possible mechanism relates to the change of the
competition between the single-ion magnetic anisotropy and the
Dzyaloshinsky-Moriya (DM) interaction with increasing x. Finally, the strong
spin-orbital coupling has been observed at temperature just above T$_N$ in
La$_{0.2}$Y$_{0.8}$VO$_{3}$ and a short range spin-orbital correlation is
suggested.
