Abstract: The coefficient k.sub.1 of linear expansion in a temperature range from 50.degree. to 300.degree. C. of a non-magnetic support member of a recording medium, before a Co-Cr alloy film is formed thereon, is less than 0 mm/mm .degree.C., and the coefficient k.sub.2 of linear expansion in a temperature range from 50.degree. to 300.degree. C. of that support member after the Co-Cr alloy film is formed is less than 0.3.times.10.sup.-5 mm/mm .degree.C. The alloy film also includes carbon in the magnetic layer, and a protective film comprised of carbon is further formed on the magnetic layer. The recording medium is particularly adapted for perpendicular magnetic recording.