Dot arrays of <i>L</i>1-type FePt ordered alloy perpendicular films fabricated using low-temperature sputter film deposition

Abstract

Using ultrahigh vacuum sputter film deposition, we fabricated L10-type Fe50Pt50 ordered alloy perpendicular films on MgO(001) single-crystal substrates and 2.5 in. glass disks at low substrate temperatures of 200–350 °C. Then we examined the magnetic properties of the dot arrays made from these films. The uniaxial magnetic anisotropy Ku for L10-type FePt films (10 nm in thickness) deposited with a Pd underlayer on MgO(001) substrates reached about 2 × 107 erg/cm3 at the substrate temperature Ts of 200 °C, and 3 × 107 erg/cm3 at Ts = 250 °C. The order parameter S was about 0.46 at Ts = 300 °C. Moreover, Ku for L10-FePt films fabricated on glass disks using MgO/Cr underlayers shows 3.4 × 107 erg/cm3 at Ts = 300 °C, which was almost equal to that for FePt single-crystal films deposited on Pd/MgO(001). The switching field distribution σ/Hc for dot arrays made from L10-FePt film [5 nm in thickness, on Pd/MgO(001) at Ts = 250 °C] was small; σ/Hc = 0.11 for a dot diameter of 15 nm. This value was smaller than that of hcp-Co75Pt25 dot arrays (σ/Hc = 0.18). The difference was mainly attributable to the degree of the easy axis distribution. This result demonstrates the homogeneous formation of a L10-type ordered structure in the FePt layers.