First-principles prediction of the morphology of L10 FePt nanoparticles supported on Mg(Ti)O for heat-assisted magnetic recording applications

We perform first-principles calculations to predict the morphology of L10 ordered FePt nanoparticles grown on Mg(Ti)O substrates with relevance to application in heat-assisted magnetic recording (HAMR) media. We show how incorporation of Ti into MgO substrates reduces the FePt adhesion energy from −1.29 (pure MgO) to −2.35 J/m2 (pure TiO). This effect is due to the formation of strong Fe-Ti bonds at the interface. Consistent with experimental observations, the predicted equilibrium morphology of supported FePt nanoparticles is significantly changed, corresponding to increased wetting. This behavior is undesirable for HAMR media since it promotes grain growth which limits the storage density. We show how passivation of surface Ti atoms (e.g., with MgO) is sufficient to restore the wetting observed for pure MgO substrates offering a viable strategy for optimization of next generation recording media.