Monte Carlo simulations of the site-diluted 3d XY model with superexchange interaction: Application to Fe[Se2CN(C2H5)2]2Cl–Zn[S2CN(C2H5)2]2 diluted magnets

• An XY model on a simple cubic lattice was proposed to study the pentacoordinate iron(III) molecular ferromagnet.
• A superexchange interaction was also proposed for this material.
• Good fits to the experimental results of the phase diagram have been obtained.

A simple site-diluted classical XY model is proposed to study the magnetic properties of the ferromagnetic polycrystalline Fe[Se2CN(C2H5)2]2Cl diluted with diamagnetic Zn[S2CN(C2H5)2]2. An extra superexchange interaction is assumed between next-nearest-neighbors on a simple cubic lattice, which are induced by a diluted ion. The critical properties are obtained by Monte Carlo simulations using a hybrid algorithm, single histograms procedures and finite-size scaling techniques. Quite good fits to the experimental results of the ordering temperature are obtained, namely its much less rapidly decreasing with dilution than predicted by the standard diluted 3d XY model, and the change in curvature around 86%86% of the magnetic Fe[Se2CN(C2H5)2]2Cl compound.