We searched for an optimum thermal treatment of double or quadruple layers of ͑Fe 2.5 nm/Pt 2.5 nm͒ in ordered to obtain a monolayer assembly of ordered FePt particles. It was found that by controlling the thickness, the substrate temperature, and using MgO͑100͒ substrates, monolayer assemblies of ordered FePt particles with the crystal axes ͓001͔ aligned vertically can be obtained at relatively low substrate temperatures around 400°C.