Synthetic ferrimagnetic media: effects of thermally assisted writing

Thermally assisted writing on high-coercivity synthetic ferrimagnetic media (SFM) was demonstrated using a conventional spin stand equipped with an optical head for commercial magnetooptical drives. The laser light (λ = 685 nm) was focused through a glass substrate onto a recording layer. The optical spot size was 1.1 μm and a commercial magnetic head had a writer width of ∼0.25 μm. The recording properties were measured as a function of the writing current (I_w) and the laser power (P_w). For the thermally stable medium with H_c = 6 kOe, a laser irradiation with an optimum power significantly improved the overwrite performance and the signal-to-noise ratio (SNR) values. The SNR values were improved by optimizing P_w over a wide writing current range. The improvements with the assist were found in both the signal and the noise. The media with a large dynamic coercivity value or with thick magnetic layers clearly showed the advantages with thermal assist.