In this work we report on the experimental analysis of the time decay of magnetization in the films of amorphous TbFeCo alloys for perpendicular magnetic recording. It is shown that the experimental results can be explained on the basis of the thermally activated incoherent subnetwork magnetization reversal model. Thermally activated reversal of the transition metal subnetwork and associated reversal of the antiferromagnetically coupled rare-earth subnetwork may result in effective stabilization of the net film magnetization. Experimentally obtained activation diameter value Da∼5–6 nm corresponds to the exchange length or the domain wall width in the films under study. The small activation diameter value combined with high stability factor k∼250 mean that the TbFeCo amorphous film should be capable of supporting a thermally stable perpendicular recording at over 100 Gbit/in2 recording density.

In this paper, we address important issues on the performance improvement of perpendicular magnetic recording (PMR) media, such as noise reduction by adjusting the soft magnetic underlayer (SUL) properties and recording layer and intermediate layer modifications for optimum signal-to-noise (SNR) performance. The permeability of the SUL plays a significant role in writability and SNR. Proper pinning of the SUL should be considered for reducing spike noise. A systematic comparison of alloy and oxide granular media shows that optimized oxide media can provide both better SNR and good thermal stability and is promising for high-density recording.

TbFeCo media for perpendicular magnetic recording were developed by employing a NiP underlayer that controls the magnetic properties of a TbFeCo magnetic layer. Dynamic write-read characteristics were examined using a conventional merge-type giant magneto-resistive (GMR) head originally designed for longitudinal magnetic recording. A clear magnetic transition of 450 kFCI (kilo Flux Change per Inch), a high media signal-to-noise ratio (SNR), and acceptable overwrite properties were obtained by optimizing the magnetic properties of TbFeCo films. The thermal stability of a written bit in TbFeCo film is sufficient for practical application.

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