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

Magnetic properties and microstructures of L1(1) (Co50-xCux)Pt-50 films sputter-deposited at 350 degrees C on MgO(111) substrates are reported. The addition of Cu significantly improves the alignment of c-axis and chemical ordering. Perpendicular coercivity (H-c perpendicular to) 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 L1(1) crystal domain. Therefore, an intermediate value of H-c perpendicular to 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. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3520662]