MONTE-CARLO CALCULATIONS ON A LATTICE WITH RANDOM SPIN INTERACTIONS

A Monte Carlo procedure is introduced in which spin-flip dynamics are applied to a system that is characterized through random radial depend ence of the exchange interaction. Application is made to a dilute syst em such as P in Si, where a topological distribution of spin orientati on affects the measured magnetic susceptibility. Although a transition temperature is not clearly defined, a Curie-Weiss description is poss ible, the nature of which can still characterize the concentration of spins in the material. The spin dynamics does not directly reveal evid ence of spin clustering and is not a valid approach below the transiti on temperature where quantum molecular effects dominate.