Monolayer CoPt magnetic nanoparticle array using multiple thin film depositions

Abstract

A monolayer of L1(0) CoPt nanoparticles was prepared on a polyimide film by depositing Co-Pt and annealing the resulting film stack at 650-800 degrees C. To obtain well-separated magnetic nanoparticles avoiding substantial coarsening often seen on annealing of thicker films, a multiple deposition of thinner Co-Pt alloy films with intentionally increased Co composition was employed. The multiple depositions relying on heterogeneous nucleation on the preexisting CoPt nanoparticles allowed the average particle size to increase from 4 to 7 nm. The monolayer of 7 nm sized CoPt nanoparticles exhibited a coercivity of 9.8 kOe with a remanence ratio of 0.72.