Investigations on annealed Ni-P in Al-Mg/Ni-P substrates as soft underlayer for perpendicular recording media

The amorphous Ni-P layer in the Al-Mg substrates of longitudinal recording media have been annealed to form soft magnetic underlayer for perpendicular recording media. After annealing at about 300 °C for 10 min, the Ni-P layer crystallized and was found to have Ni3P and Ni phases. The annealed samples were found to have soft magnetic properties. As the annealing temperature was increased, the samples showed a larger coercivity. The optical surface analyzer (OSA) results indicated that crystallized Ni-P could show lower noise than sputtered Ni-Fe thin films.