Large uniaxial magnetocrystalline anisotropy for Co₅₀Pt ₅₀ disordered alloy films with hexagonal-close-packed stacking structure by substituting Pt with Rh

In order to increase the uniaxial magnetocrystalline anisotropy constant (K_u) of a Co₅₀Pt₅₀ film, CoM(M = Pt, Pd, Rh) disordered films are investigated with respect to stacking faults (SFs) in hexagonal-close-packed (hcp) grains. The Co₅₀Rh₅₀ film was revealed to have nearly perfect hcp stacking, while the Co₅₀Pt ₅₀ and Co₅₀Pd₅₀ films contain SFs. Therefore, Pt atoms in the Co₅₀Pt₅₀ films were replaced by Rh atoms to enhance K_u by decreasing the density of SFs. The Co ₅₀(Pt₁-rRh_r)₅₀ film with r = 0.5 showed a maximum K_u of nearly 1 × 10⁷ erg cm ^-3, which is around 10 times larger than that for the Co ₅₀Pt₅₀ film.