In this work, the critical phenomena of Nickel II Iron III oxide (Ferromagnetic) shall be determined using Monte Carlo simulation technique. The critical temperature (Tc), the magnetization per site (?), energy per site (E), magnetic susceptibility (?), specific heat of a NiOFe2O3 are determined as a function of temperature for two different square lattices 20x20 and 150x150. The analysis of simulation results indicates that the bipolar magnet with strong tetragonal distortion in external magnetic field applied along the axis resembles the behaviour of the two dimensional Ising model on the rectangular lattices. The numerical solution of the model in MATLAB "R2013a" is presented. For the sake of clarity, a Monte Carlo Algorithm known as Metropolis Hastings Algorithm was used to evaluate the behaviour of the lattice and the critical temperature at which the phase transition between NiOFe2O3 and paramagnetic state occurs was noted. The analysis of the results shows that Tc = 2.25J/KB , in the absence of external magnetic field. It was observed that above (Tc) the material (NiOFe2O3) becomes a paramagnetic state, and this leads to decreasing in average magnetization and the average Energy increases, while below (Tc) the material is in a ferromagnetic state.