Domain wall displacement detection (DWDD) with land-groove recording for achieving 30 Gbit/inch2

The authors previously studied domain wall displacement detection (DWDD) (T. Shiratori et al, J. Mag. Soc. Jpn., vol. 22, supp. no. S2, pp. 47-50, 1998) with land-groove recording and reported successful recording at 20 Gbit/inch² areal density (T. Sakamoto et al, Tech. Dig. ODS 2001, MD8, pp. 73-75, 2001). The technical approach for huge capacity with DWDD is decided according to the method for shortening the track pitch. When groove or land-recording is chosen, it is difficult to prepare quality substrates for good signals and to obtain stable tracking. When land-groove recording is chosen, the most difficult problem is to obtain a sufficiently wide recording power margin. The authors studied DWDD in more detail and clarified the necessary conditions for improvement of DWDD using the reverse rotation readout method. In this paper, we show and explain some interesting experimental results of laser power margins in the case of land-groove recording. The results raise the possibility of 30 Gbit/inch² DWDD and some ideas are discussed at the end of this paper.