Magnetic Anisotropy of Co-M-Pt ( ${\rm M}={\rm Cr}$ , Mo, Ru, W, Re) Perpendicular Films Deposited on Various Seed Layer Materials

The first and second order uniaxial magnetic anisotropy, K_u1 and Ku2, and the saturation magnetization, M_s, of (Co _100-XM_X)_100-YPt_Y perpendicular thin films were examined, in order to improve the magnetic properties of CoCrPt-SiO₂ media by replacing Cr with M. Fourteen kinds of M elements were examined, but we mainly focus on films with M=Cr, Mo, Ru, W and Re in this paper, since the other elements significantly reduced Ku1,Ku2 or the K_u/M_s ratio. The use of the M elements, instead of Cr, did not result in any significant increase in the values of K_u1, K_u2, and the Ku/M_s ratio. On the other hand, K_u1 and K _u2 of CoPt binary films had a greater dependence on the seed layer materials used (Ru, Pd, Re, Pt, Au, Ir and Cu). The c/a ratio of the hcp-CoPt lattice varied significantly with the seed layer materials used probably due to the epitaxial growth of CoPt. K_u1 decreased and K_u2 increased as the c/a ratio increased. The use of specific seed layer materials was more effective at controlling the magnetic anisotropy of CoPt based perpendicular thin films, rather than the addition of M element to the CoPt