Magnetic media with ferromagnetic overlay materials for improved thermal stability

A magnetic recording disk comprising:

• a) a disk substrate;
• b) an underlayer comprising Cr deposited on said disk substrate;
• c) a granular ferromagnetic host layer comprising a Co alloy comprising CoxCry wherein 20<x<85 and 0<y<30 atomic percent, and 40<(x+y)<90;
• and
• d) a ferromagnetic overlay comprising at least one element selected from the group consisting of Cou, Fev and Niw wherein 0<u<100, 0<v<100 and 0<w<100 atomic percent, and 50<(u+v+w)<100 atomic percent, wherein said ferromagnetic overlay has an effective thickness of 1.0 to 40 Angstroms and is in contact with said host layer, and wherein said ferromagnetic host layer is a discontinuous layer.

A method of making a magnetic recording medium, said method comprising the steps of:

• a) providing a substrate;
• b) depositing an underlayer on said substrate;
• c) depositing a granular ferromagnetic Co alloy host layer on said underlayer with a thickness in the range of approximately 1 to 30 nanometers;
• and
• d) depositing a ferromagnetic overlay on said granular ferromagnetic Co alloy host layer, said ferromagnetic overlay comprising at least one element selected from the group consisting of Co, Fe and Ni and having an effective thickness in the range of approximately 1 to 40 Angstroms and a magnetic moment density at least 1.5 times greater than the magnetic moment density of said granular ferromagnetic Co alloy host layer.