To overcome the high sensitivity of the signal-to-noise ratio (SNR) to the switching field distribution in the perpendicular media, we proposed to use tilted media in the perpendicular recording system in this letter. It was found that a much better tolerance of the easy-axis distribution could be achieved when tilted media were used instead of perpendicular media in a perpendicular recording system. We then analyzed the range of the switching field at the freezing points, and found that high Ku magnetic material is feasible in tilted media. The results indicated that the areal density could be more than 62% higher than that of perpendicular media when 45° easy-axis tilted media with Ku=7.0×106 erg/cm3 were used. Finally, simulation of the switching dynamics revealed that a much faster magnetization switching could be achieved in 45°-tilted media than in perpendicular media.

In this paper, we systematically present the fundamental understandings of advantages of tilted magnetic recording. We investigate the various configurations of tilted magnetic recording including tilted longitudinal recording, tilted perpendicular recording with tilted media and normal single pole head, and tilted perpendicular recording with perpendicular media and tilted writing head. Tilted media with easy axis along the down-track and cross-track directions and tilted media with varied in-plane orientation ratios have been investigated and compared in detail. One important finding is that slight oriented (in-plane) tilted media shows a tremendous improvement in recording performance, which may release the pressure on the fabrication of perfect tilted hard disk magnetic media. Various fabrication methods for tilted media have also been discussed.

The effect of thermal energy (kBT), which has been found to play some important roles in the magnetic properties of recently developed antiferromagnetically coupled media, is described. It was observed that the thermal energy helps to obtain an antiparallel configuration of moments at remanence. Therefore, a reduction in the remnant moment–thickness product (Mrδ) is observed, even for smaller values of J (interface coupling constant) than those used in simulations that do not consider thermal energy. The magnetic viscosity measurement helps to distinguish the magnetization decay behavior of the top and bottom layers. The magnetic moments of top and bottom layers show maximum decay at different fields and the decay rates approximately scale with their thickness. Viscosity results also point out that the magnetization reversal of the bottom layer should occur in the first quadrant, in order to obtain a low noise and thermally stable media. Micromagnetic simulation was performed by including thermal effects. In that case, Mrδ reduction could be obtained for smaller values of J than in the case where thermal energy is not included in the simulation.

In this article, we have studied the potential of tilted media to extend the longitudinal recording density via micromagnetic simulation. The magnetization reversal mechanism is systematically analyzed to determine the angular dependence of coercivity of this media. Such a characteristic determines the recording performance for different recording directions. A sharp transition is observed for the good recording direction. In contrast, large transition noise is observed for the bad recording direction. Tilted media have the advantage similar to the perpendicular media for extreme high recording density, resulting from the use of high Ku and low demagnetization field at the transition. Most importantly, the magnetization in the tilted configuration can be reversed effectively with a longitudinal ring head.

Experimental methods to obtain remnant moment-thickness product (Mrδ) reduction in the laminated antiferromagnetically coupled (LAC) recording media is described. The results indicate that the reduction in Mrδ (or, indirectly, a reduction in noise) can be obtained by altering the antiferromagnetic coupling constant J, or by the parameters of the underlayer such as anisotropy constant (Ku2), thickness (t2), etc. A method to enhance J by intrinsic means is proposed by which a high exchange field of about 1900 Oe can be obtained. Thermal energy has been found to help in obtaining a Mrδ reduction in LAC media. Substrates with lower surface roughness also enhance the Mrδ reduction.