I. Introduction
The L10-FePt-based thin films with a (001) crystallographic texture have been largely investigated over the last two decades as potential materials for next generation ultra-high density magnetic recording media (>1 Tbit/in2), due to the high magnetocrystalline anisotropy (5–10 MJ/m3), which ensures the room temperature thermal stability of grains with in-plane size down to 3 nm [1]–[7]. Moreover, due to the moderate Curie temperature (650–750 K) of the FePt-based alloys, such a material is currently the best candidate for heat-assisted magnetic recording (HAMR), an emergent technology close to the commercialization, which is expected to increase the areal density in hard disk drives beyond 2 Tbit/in2 [8]. To achieve thermally stable recording media for HAMR with an area density as large as 2 Tbit/in2, FePt granular films consisting of columnar and well-separated grains with a high microstructural uniformity and small in-plane size are required. For this purpose, single and multiple segregants such as carbon [9], transition metal–oxide [10]–[14], and carbide [15] have been extensively discussed but further work is still necessary to achieve the required morphostructural and magnetic properties for recording densities up to 2 Tbit/in2 and beyond. In this paper, a novel Mg(Ti, Ta, Zr, Nb, B)O multiple-oxide segregant material consisting of higher and lower melting point oxides with different segregation abilities was explored to obtain separated and uniform FePt grains by exploiting the higher and lower diffusion rates of different oxides [16].