MAGNETIC, MAGNETOOPTICAL AND DYNAMIC CHARACTERISTICS OF EXCHANGED-COUPLED NDTBFECO TBFECO FILMS FOR 532 NM RECORDING MEDIA/

A magnetic, magneto-optical and structural study was performed on exch anged-coupled(EC) layers between NdTbFeCo and TbFeCo films for a 532 n m recording media. The saturation magnetization (Ms) of separate RO an d ST film varied from 177 to 269 emu/cm(3), and from 73 to 87 emu/cm(3 ), respectively, in sputtering power range of 0.4 to 0. 73 kW at a fix ed Ar gas flow rate. Coercivity (Hc) and Kerr angle (theta k) of RO ra nged between 0.46 kOe and 0.65 kOe, and between 0.34 degrees and 0.38 degrees, respectively in Ar gas flow rate range of 15 to 40 sccm, and no great changes were found in the surface morphologies, as observed w ith an atomic force microscopy (AFM). Hc and squareness rose from 2 kO e to 6 kOe and 0.6 to 0.98 with increasing R from 1.5 to 8, where R is the thickness ration of NdTbFeCo to TbFeCo (total thickness 200 Angst rom, 250 Angstrom) in the five layered SiNx/NdTbFeCo/TbFeCo/SiNx/Al-Ti . The carrier-to-noise ration (CNR) increased by about 8 dB, as R was raised from 1.5 to 3. The films were prepared by the magnetron rf-dc, continuous sputtering system. No atomic mixing between NdTbFeCo and Tb FeCo layer occurred, as confirmed by TEM cross sectional observations.