Enhancement of perpendicular coercivity in L11 CoPt thin films by replacement of Co with Cu

Abstract

Magnetic properties and microstructures of L11 (Co50−xCux)Pt50 films sputter-deposited at 350 °C on MgO(111) substrates are reported. The addition of Cu significantly improves the alignment of c-axis and chemical ordering. Perpendicular coercivity (Hc⊥) also increases markedly from 0.1 to 1.9 kOe while in-plane coercivity declines from 0.5 to 0.07 kOe for the 20 nm thick films at x=26. Similar phenomena are observed with larger effects for the 50 nm thick films. The coercive mechanism is attributed to domain-wall pinning produced by the compositional segregation of nanoscaled nonmagnetic Cu-rich and magnetic Co-rich regions within a coherent L11 crystal domain. Therefore, an intermediate value of Hc⊥ can be obtained from this hardening mechanism when further microstructure modifications are enforced, which largely increases the potential for the use in spintronic devices or patterned media.