Magnetic tape device and head tracking servo method

A head tracking servo method comprising:

• reading a servo pattern of a magnetic layer of a magnetic tape by a servo head in a magnetic tape device,
• wherein the servo head is a magnetic head including a tunnel magnetoresistance effect type element as a servo pattern reading element,
• the magnetic tape includes a non-magnetic support, and a magnetic layer including ferromagnetic powder, a binding agent, and fatty acid ester on the non-magnetic support,
• the magnetic layer includes the servo pattern,
• a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 2.0 nm,
• a full width at half maximum of spacing distribution measured by optical interferometry regarding the surface of the magnetic layer before performing a vacuum heating with respect to the magnetic tape is greater than 0 nm and equal to or smaller than 7.0 nm,
• a full width at half maximum of spacing distribution measured by optical interferometry regarding the surface of the magnetic layer after performing the vacuum heating with respect to the magnetic tape is greater than 0 nm and equal to or smaller than 7.0 nm,
• a difference Safter−Sbefore between a spacing Safter measured by optical interferometry regarding the surface of the magnetic layer after performing the vacuum heating with respect to the magnetic tape and a spacing Sbefore measured by optical interferometry regarding the surface of the magnetic layer before performing the vacuum heating with respect to the magnetic tape is greater than 0 nm and equal to or smaller than 8.0 nm, and
• a ratio Sdc/Sac of an average area Sdc of a magnetic cluster of the magnetic tape in a DC demagnetization state and an average area Sac of a magnetic cluster of the magnetic tape in an AC demagnetization state measured with a magnetic force microscope is 0.80 to 1.30.