A magnetic recording medium includes a substrate (4), an overcoat layer (16) and a magnetic layer (14) therebetween. The magnetic layer contains cobalt and the overcoat layer contains carbon, as is conventional. The outer surface (20) of the magnetic layer is treated with an oxygen-containing plasma; the overcoat layer is then applied to the treated outer surface. The oxygen-containing plasma is typically a mixture of oxygen and argon, although other oxygen-containing mixtures could be used as well. This surface treatment results in improved magnetic properties and recording performance values.