Uniaxial magnetocrystalline anisotropy for c -plane oriented Co _100-xM_x (M: Cr, Mo, W) film with stacking faults

Stacking faults (SFs) in Co-based alloy grains in a Co100-x Mx (M: Cr, Mo, and W) film are evaluated by means of in-plane x-ray diffraction. Moreover, the correlation between SFs and uniaxial magnetocrystalline anisotropy Ku is discussed in connection with the spin-orbit interaction. The ratio of the integrated intensities of the (10.0) to (11.0) diffractions corrected by Lorentz and atomic scattering factors has been proposed as an index for SFs in hcp films with a c -plane sheet texture. This ratio is equal to 0.25 for perfect hcp stacking, while it is 0 for perfect fcc specific stacking. It has a one-to-one correspondence with the probability of - A-B-C - atomic-layer stacking Pfcc. Using this index, pure sputtered Co films are found to have a Pfcc of 10%. The addition of only 5 at. % of Mo or W into the Co grains reduces Pfcc to 2%. Ku was found to increase with the addition of material (e.g., Ku was 4.0× 106 ergs/ cm3 for 5 at. % Mo), although the atomic magnetic moment of Co decreases monotonously. A Pfcc of 10% is found to lower Ku in a pure Co film by more than a factor of 2 when the spin-orbit interaction is taken into account.