Intrinsic and hysteresis properties of FePt nanoparticles

Abstract

This comprehensive study examines the effect of particle size and atomic ordering on the intrinsic and hysteresis properties of FePt nanoparticles embedded in a carbon matrix formed by annealing sputtered FePt/C multilayer precursors. Structural studies show a transformation from the magnetically soft to the tetragonal FePt phase dependent on the annealing conditions. The magnetic properties scale as a function of particle size. The coercivity depends, in part, on the vol % of carbon and develops with annealing as a result of increased atomic ordering. Under the right conditions a high coercivity of 34 kOe has been achieved. Remanence curves show a variation of interparticles interactions from exchange to magnetostatic with increasing vol % carbon. Time dependent measurements indicate a decrease of the activation volume converging to the actual particle size (determined by TEM) as the carbon content is increased. The potential for future magnetic recording media is discussed.