Conversion of FeCo from soft to hard magnetic material by lattice engineering and nanopatterning

TLDR: The hard magnetic properties and magnetic domain structures of nanopatterned FeCo alloy thin films are experimentally investigated and a relatively large value of the perpendicular uniaxial magnetic anisotropy Ku = 2.1 × 106 J·m−3 was obtained, while the Hc of the nanopatting FeCo layers increased with decreasing dot pattern size.

Abstract: The development of magnetic materials with large uniaxial magnetic anisotropy (K u) and high saturation magnetization has attracted much attention in various areas such as high-density magnetic storage, spintronic devices, and permanent magnets. Although FeCo alloys with the body-centred cubic structure exhibit the highest M s among all transition metal alloys, their low K u and coercivity (H c) make them unsuitable for these applications. However, recent first-principles calculations have predicted large K u for the FeCo films with the body-centred tetragonal structure. In this work, we experimentally investigated the hard magnetic properties and magnetic domain structures of nanopatterned FeCo alloy thin films. As a result, a relatively large value of the perpendicular uniaxial magnetic anisotropy K u = 2.1 × 106 J·m−3 was obtained, while the H c of the nanopatterned FeCo layers increased with decreasing dot pattern size. The maximum H c measured in this study was 4.8 × 105 A·m−1, and the corresponding value of μ 0 H c was 0.60 T, where μ 0 represented the vacuum permeability.