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 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
• ΔSFD in a longitudinal direction of the magnetic tape calculated by Expression 1 is equal to or smaller than 0.50,
• ΔSFD=SFD25° C.−SFD−190° C. Expression 1
• in Expression 1, the SFD25° C. is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25° C., and the SFD−190° C. is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −190° C.