Electroless plated disks for perpendicular magnetic recording

Co-Ni-Mn-Re-P perpendicular recording disks were prepared by the electroless plating method using newly developed plating baths. Typical magnetic properties on the disks were the anisotropy energy Ku= -0.95 × 105 ~2.2 × 105erg/cc, coercivity Hc(⊥)=440~1270 Oe and saturation magnetization Ms=104~252 emu/cc. Recording performance on these disks was evaluated by using Winchester heads under practical head-medium spacing. Perpendicular recording mode and 51k FRPI (2000 FRPM) linear density as D50 were obtained with 0.5 µm thick medium disk and 0.33 µm gap length head at 0.2 µm head-medium spacing. SNR and the overwrite characteristics were better than 26 dB and 30 dB, respectively, at 51k FRPI and 18 µm track width. It was found that overwrite characteristics becomes worse as Ku increases from negative values to positive values, while recording density D50 slightly increases in the same Ku region. Further, higher recording density, D50=68k FRPI (2700 FRPM), was attained by decreasing the medium thickness and head-medium spacing to 0.2 µm and 0.12 µm, respectively. These electroless plated disks have a high potential for use as perpendicular recording media.