  In this work we study a disordered binary Ising model on the square lattice.
The model system consists of two different particles with spin-1/2 and spin-1,
which are randomly distributed on the lattice. It has been considered only spin
nearest-neighbor exchange interactions with $J>0$. This system can represent a
disordered magnetic binary alloy $A_{x}B_{1-x}$, obtained from the high
temperature quenching of a liquid mixture. The results were obtained by the use
of Monte Carlo simulations for several lattice sizes $L$, temperature $T$ and
concentration $x$ of ions $A$ with spin-1/2. We found its critical temperature,
through the reduced fourth-order Binder cumulant for the several values of the
concentration $x$ of particles (spin-1/2, spin-1), and also the magnetization,
the susceptibility and the specific heat as a function of temperature $T$.
