Patent ID: 7465501

Claim:
A longitudinal magnetic recording medium comprising at least four magnetic layers comprising: a substrate, a CoCrTa magnetic intermediate layer on the substrate, wherein the CoCrTa magnetic intermediate layer comprises Cr<16 at % and Ta<6 at %, a first CoCrPtB magnetic layer on the CoCrTa layer, wherein the first CoCrPtB magnetic layer comprises Cr: 10-14%, Pt: 4-8 at %, B: 6-10%, a second CoCrPtB magnetic layer on the first CoCrPtB magnetic layer, and a third CoCrPtB magnetic layer on the second CoCrPtB layer, wherein the third CoCrPtB magnetic layer comprises Cr: 12-16 at %, Pt: 12-16 at %, B: 10-14 at % and has <10 at % Cr than that in the second CoCrPtB magnetic layer, wherein the magnetic intermediate layer has a different composition than that of the first, second and third magnetic layers, wherein the second CoCrPtB magnetic layer comprises Cr: 22-26 at %, Pt: 11-15 at % and B: 4-8 at %.