Patent ID: 7141316

Claim:
A perpendicular magnetic recording medium comprising: a nonmagnetic substrate, a soft magnetic layer formed on the nonmagnetic substrate; first undercoating layer formed on the soft magnetic layer, a second undercoating layer formed on the first undercoating layer and having crystal grains and grain boundary region separating the crystal grains, and a perpendicular magnetic recording layer formed on the second undercoating layer, wherein the first undercoating layer contains at least one of the same elements forming the crystal grains of the second undercoating layer, the crystal grains contain at least one element selected from the group consisting of Pt, Ru, Y, Pd, Re and Rh, and the grain boundary material contains at least one boride selected from the group consisting of AlB 2 , HfB 2 , MoB 2 , NbB, NbB 2 , TaB, TaB 2 , TiB 2 , VB 2 , WB, ZrB 2 , CrB, Crb 2 , CeB 6 , LaB 6 and SmB 6 .