Magnetic recording medium

A magnetic recording medium, comprising:

• a substrate;
• an underlayer disposed on the substrate;
• and
• a magnetic layer disposed on the underlayer,
• wherein the substrate includes a polyester,
• the magnetic recording medium includes a lubricant,
• the magnetic layer has a surface including a plurality of holes,
• an arithmetic average roughness Ra of the surface of the magnetic layer is 2.5 nm or less,
• a BET specific surface area of the magnetic recording medium measured in a state where the magnetic recording medium has been washed and dried is 3.5 m2/g or more and 7.0 m2/g or less,
• a squareness ratio of the magnetic layer in a longitudinal direction is 35% or less,
• an average thickness of the magnetic layer is 80 nm or less,
• an average thickness of the magnetic recording medium is 5.6 µm or less,
• a servo pattern is recorded on the magnetic layer and a statistical value σsw indicating a non-linearity of the servo pattern is 24 nm or less, and
• the statistical value σsw is defined by:
• σ
• sw
• =
• ∑
• WIP
• f
• ×
• df
• ­­­(1)
• where WIP(f) is a displacement difference during actual drive and df is a wave number interval.