Dhia`a K. Khudier, Nabeil I. Fawaz, Ising Model Phase Transition Calculation for Ferro-Paramagnetic Lattice, ILCPA Volume 15, International Letters of Chemistry, Physics and Astronomy (Volume 15) https://www.scipress.com/ILCPA.15.201 Abstract: The position of the phase transition in the two dimensional Ising model were determined byusing Monte Carlo simulation in a quadratic for area of variable length with external magnetic fieldswitched off (<i>B</i> = 0). The magnetization<i> (M)</i> per site<i> (µ)</i>, magnetic susceptibility <i>(x)</i> of aferromagnetic and paramagnetic materials were calculated as a function of temperature <i>T</i> for(20×20,40×40,60×60), (80×80,120×120,200×200) spin lattice interactions. Nearest neighborinteraction is assumed (i.e. each spin has 4 neighbors); uses periodic boundary conditions. The Curietemperature (<i>T<sub>c</sub> = 2.27 J/k<sub>B</sub></i> ) is determined by measuring the magnetic susceptibility at which theferromagnetic and paramagnetic undergoes a phase change from order to disorder. There is thus aphase transition defined by the Curie temperature. The Monte Carlo method were used to check theseresults and to confirm the phase transition. The data are analyzed using the Curie-Weiss law whichcontains the Curie temperature as a parameter. Keywords: Ferromagnetic Materials, Magnetic, Monte Carlo Simulation