  We have used the Sagdeev pseudo-potential technique to investigate the
arbitrary amplitude ion acoustic solitons, double layers and supersolitons in a
collisionless magnetized plasma consisting of adiabatic warm ions, isothermal
cold electrons and nonthermal hot electrons immersed in an external uniform
static magnetic field. We have used the phase portraits of the dynamical system
describing the nonlinear behaviour of ion acoustic waves to confirm the
existence of different solitary structures. We have also investigated the
transition of different solitary structures: soliton (before the formation of
double layer) $\rightarrow$ double layer $\rightarrow$ supersoliton
$\rightarrow$ soliton (soliton after the formation of double layer) by
considering the variation of $\theta$ only, where $\theta$ is the angle between
the direction of the external uniform static magnetic field and the direction
of propagation of the wave.
