Coupled granular/continuous medium for thermally stable perpendicular magnetic recording

We studied coupled granular/continuous (CGC) perpendicular media consisting of a continuous multilayer structure and a granular layer. The addition of Co/Pt multilayers decreased the nucleation field from 200 to -1800 Oe and increased the squareness from 0.9 to 1.0. The moment decay at room temperat ure was significantly reduced from -4.8% to -0.05 % per decade. At elevated temperatures, strong exchange coupling between a granular layer and a cont inuous layer is needed for thermal stability. The exchange-coupled continuo us layer reduces thermal demagnetization as it effectively increases the gr ain size, tightens the grain distribution, and prevents the reversal of ind ividual grains. Magnetic Force Microscope image showed a larger magnetic cl uster size for the CGC structure. Compared to the CoCr18Pt12 medium, the CG C medium had 2.3 dB higher output. However, the noise for the CGC medium in creased with the recording density, while the noise for the CoCr18Pt12 medi um remained constant from 4 to 15 kfc/mm. Further optimization and noise re duction are still required for future high density recording. (C) 2001 Else vier Science B.V. All rights reserved.