Spacer-less, decoupled granular L1 FePt magnetic media using Ar–He sputtering gas

Abstract

Spacer materials are often used to fabricate granular L10 FePt media and reduce the grain size, however, at the expense of reduced out-of-plane coercivity. Here, we demonstrate a spacer-less method in which adding 1% helium to argon sputtering gas leads to a substantial improvement in the chemical ordering, as well as the magnetic and microstructural properties of FePt. This change is attributed to the modification in the ion current density of the plasma caused by the excited metastable helium species. Helium plays a pivotal role in providing the Fe and Pt atoms optimal adatom mobility, thereby, producing well-ordered L10 FePt media. This leads to an enhancement of the out-of-plane coercivity from 15 to 22 kOe. Furthermore, exchange decoupled grains with a twofold reduction in their diameter to ∼24 nm are also achieved. These properties are crucial for magnetic media of the future for data storage recording densities beyond 1 Tb/in2.