Effect of Pt on the magnetic anisotropy and intergranular exchange coupling in (Co₈₆Cr₁₂Ta₂)_100-xPt_x and (Co_62.5Ni₃₀Cr_7.5)_100-xPt_x thin-film media

The effect of Pt on the magnetic anisotropy of grains and intergranular exchange coupling in (Co₈₆Cr₁₂Ta₂)_100-xPt_x (x = 1-8) and (Co_62.5Ni₃₀Cr_7.5)_100-xPt_x (x = 0-16) thin-film media has been investigated. In both kinds of media, the magnetocrystalline anisotropy field of the grains, H_k^grain, increases to twice as large as that at x = 0 by increasing x to about 9 at%. This is caused mainly by an increase in the magnetocrystalline anisotropy of the grains. The coercive force H_c increases with increasing Pt content, due mainly to the increase in H_k^grain, although H_c/H_k^grain gradually decreases with increasing Pt in these media. In the CoCrTaPt media, the decrease in H_c/H_k^grain with increasing Pt is caused mainly by an increase in the strength of the intergranular exchange coupling. In the CoNiCrPt media, the change in the c-axis direction from in-plane to normal with increasing Pt is suggested to play a major role in the reduction of H_c/H_k^grain.