ENHANCED SUPERPARAMAGNETISM IN 2-DIMENSIONAL ARRAYS OF NANOMETER-SIZED FE ISLANDS

Iron grown on room-temperature CaF2/Si(111) substrates form two-dimens ional arrays of nanometer-sized superparamagnetic islands. Deposition of Ag on the Fe/CaF2/Si(111) produced a superparamagnetic response whe re the effective moment was proportional to the number of Fe islands c overed by an average-sized Ag island. The nonmagnetic Ag overlayer med iates a long-range exchange between neighboring Fe islands within an i ndividual Ag island. Monte Carlo methods are used to examine ordering in two dimensions and to set minimum interisland coupling strengths. ( C) 1995 American Institute of Physics.