  We study the magnetic properties of a mixed Ising ferrimagnetic system, in
which the two interacting sublattices have spins $\sigma$, $(\pm 1/2)$ and
spins $S$, $(\pm 3/2,\pm 1/2)$ in the presence of a random crystal field, with
the mean field approach. The obtained results show the existence of some
interesting phenomena, such as the appearance of a new ferrimagnetic phase
namely the partly ferrimagnetic phase $(m_{\sigma}=\frac{-1}{2},m_S=+1)$ and
consequently the existence of three topologically different types of phase
diagrams. The effect of increasing the exchange interaction parameter $J$, at
very low temperature is investigated. The transitions shown in these phase
diagrams are in good agreement with those obtained in the ground state case.

Statistical Mechanics