Magnetic properties of Fe/Ti multilayered films for a magnetic recording medium

Films with combinations of Fe and Ti layers of various thicknesses (d_Fe of 10~1000 Å and d_Ti of 10~200 Å) have been prepared at Ar gas pressure of 2 mtorr in an apparatus with two pairs of facing-target sputtering sources. The total thickness of the Fe layers was fixed at 1000 Å for all specimen films. The saturation magnetization 4πM_s calculated from the expected total thickness of Fe layers decreased first gradually and then abruptly with d_Fe, becoming almost zero at d_Fe of about 15 Å for all as-deposited films. The coercive force, H_c, increased with decreasing d_Fe, taking a maximum value of 270 Oe at d_Fe of 20 Å, and decreased abruptly with further decrease of d_Fe. The films with modulation period of Fe(52 Å)/Ti(53 Å) which were annealed at temperatures above 200°C had smaller 4 πM than the as-deposited ones and H_c as high as 650 Oe at 230~325°C. Films with this modulation period annealed at about 250°C could be used as a magnetic recording medium because they have relatively large average 4πM_s of 4 kG, H _c of 650 Oe, moderate squareness of 0.7, and coercivity squareness of 0.8