Disclosed is a magnetic disk which has a lubricant layer with excellent heat resistance and high adhesiveness and is free from fly-stiction failure or corrosion failure even at an extremely low flying height of 10 nm or lower. Also disclosed is a magnetic disk which has a lubricant layer with good thermal properties and can exert a stable action over a wide temperature range. The magnetic disk comprises a substrate ( 1 ), and a magnetic layer ( 3 ), a carbon-containing protective layer ( 4 ) and a lubricant layer ( 5 ) provided on the substrate ( 1 ), wherein the lubricant layer ( 5 ) contains a magnetic disk lubricant comprising a compound having a phosphazene ring and two or more hydroxyl and/or carboxyl groups in the molecule.
1. A magnetic disk having a magnetic layer, a carbon-based protective layer, and a lubricating layer over a substrate, wherein:
the magnetic disk is adapted to be mounted in a magnetic disk apparatus of a load unload system having a magnetic head flying height of 10 nm or less, and
the lubricating layer contains a phosphazene compound represented by a general formula (I), the phosphazene compound having a phosphazene ring
(in the formula, at least one of R 1 to R 6 is a group having a perfluoropolyether main chain represented by —(O—C 2 F 4 )m-(O—CF 2 )n- (m and n are each an integer of 1 or more) and at least two carboxyl groups in the perfluoropolyether main chain, and
the remaining of R 1 to R 6 are respectively fluorine-containing groups, and three or more carboxyl groups are present in one molecule of the phosphazene compound).
2. A magnetic disk according to claim 1 , wherein a number-average molecular weight (Mn) of the phosphazene compound is 300 to 7000.
3. A magnetic disk according to claim 1 , wherein m+n in the —(O—C 2 F 4 )m-(O—CF 2 )n- falls within a range of 2 to 80.