RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To ensure sufficient durability and corrosion resistance even if a protective layer has a thickness of a specified value or less by providing a first protective layer substantially containing no grain having grain size of specified value or above, and a second protective layer containing grains having grain size of specified range formed on the first protective layer. SOLUTION: A protective layer of 10 nm or thinner being provided on the surface of a magnetic layer comprises first and second protective layers formed of grains having different grain size. The first protective layer substantially contains no grain having grain size of 1 nm or above. The second protective layer is formed on the surface of the first protective layer and contains grains having grain size of 1-3 nm. Since the grains in the first protective layer have grain size less than 1 nm, gap is eliminated at grain boundary and corrosion resistance is enhanced under high temperature high humidity conditions. Grain size of the second protective layer is prescribed at 1-3 nm on the lubricant side from the viewpoint of holding the lubricant on the protective layer. Density ratio between the first and second protective layers is suitably set in the range of 4:3-2:1.