New high performance magneto-optic media: Tb/Bi/FeCo and Tb/Pb/FeCo superlattices (invited)

Tb/Bi/FeCo and Tb/Pb/FeCo superlattices are demonstrated to offer Kerr rotation and figure of merit (reflectivity times Kerr rotation) substantially exceeding that offered by conventional TbFeCo recording materials, particularly at blue wavelengths. Superlattices such as 4.4 Å Tb/2.0 Å Bi/5.0 Å Fe_0.6Co_0.4 exhibit squarenesses suitable for magneto-optical recording and figure of merits of 0.20, 0.18, and 0.14 at wavelengths of 780, 650, and 430 nm, respectively. Dynamic testing with 780 and 490 nm light demonstrates that the high figures of merit translate to carriers several dB above those produced by TbFeCo alloys. Furthermore, very high carrier-to-noise ratios such as 54 dB at a mark length of 0.75 μm (4 MHz) and 60 dB at long mark lengths (1 MHz) are obtained using 490 nm light and a bandwidth of 30 kHz.