A magnetic recording medium is a magnetic recording medium having a tape-like shape and includes a base substrate and a magnetic layer provided on the base substrate. A plurality of data tracks can be formed in the magnetic layer, a width of a data track is 2900 nm or less, and in a case of defining, as w.sub.max and w.sub.min, a maximum value and a minimum value respectively out of average values of a width of the magnetic recording medium measured under four kinds of environment in which temperature and relative humidity are set to (10° C., 10%), (10° C., 80%), (29° C., 80%), and (45° C., 10%), w.sub.max and w.sub.min satisfy a relation of (w.sub.max−w.sub.min)/w.sub.min≤400 [ppm].

A magnetic recording medium is a magnetic recording medium having a tape-like shape and includes a base substrate and a magnetic layer provided on the base substrate. A plurality of data tracks can be formed in the magnetic layer, a width of a data track is 2900 nm or less, and in a case of defining, as w.sub.max and w.sub.min, a maximum value and a minimum value respectively out of average values of a width of the magnetic recording medium measured under four kinds of environment in which temperature and relative humidity are set to (10° C., 10%), (10° C., 80%), (29° C., 80%), and (45° C., 10%), w.sub.max and w.sub.min satisfy a relation of (w.sub.max−w.sub.min)/w.sub.min≤400 [ppm].

In the magnetic tape, a magnetic tape deformation amount after storage for 3 months each in a predetermined environment is 0.50 μm or less, a rate of a change in the magnetic tape deformation amount with respect to a change in relative humidity is 0.0001 μm/% to 0.0500 μm/%, and a rate of a change in magnetic tape deformation amount with respect to a change in temperature is 0.0010 μm/° C. to 0.1000 μm/° C.

In the magnetic tape, a magnetic tape deformation amount after storage for 3 months each in a predetermined environment is 0.50 μm or less, a rate of a change in the magnetic tape deformation amount with respect to a change in relative humidity is 0.0001 μm/% to 0.0500 μm/%, and a rate of a change in magnetic tape deformation amount with respect to a change in temperature is 0.0010 μm/° C. to 0.1000 μm/° C.

Provided are a magnetic tape comprising a magnetic layer containing a ferromagnetic powder and a binding agent on a non-magnetic support, in which the magnetic layer contains an oxide abrasive, an average particle diameter of the oxide abrasive obtained from a secondary ion image acquired by irradiating a surface of the magnetic layer with a focused ion beam is greater than 0.08 μm and 0.14 μm or smaller, and an absolute value ΔN of a difference between a refractive index Nxy measured with respect to an in-plane direction of the magnetic layer and a refractive index Nz measured with respect to a thickness direction of the magnetic layer is 0.25 to 0.40, and a magnetic recording and reproducing device including the magnetic tape.

In the magnetic tape, in a case where a maximum value of an absolute value of a difference between a servo band spacing obtained before storage, and a servo band spacing obtained after storage of N cycles, in a case where predetermined storage is set to one cycle, is defined as A, a medium life calculated by a linear function that is derived from the value of A and the value of the logarithm log.sub.eT of total storage time T of the storage of N cycles is 3 years or longer. The medium life is T in a case where the A satisfies Equation a: A=1.5−B. The B is calculated by multiplying a difference between a maximum value and a minimum value of the servo band spacings obtained in each of the five environments by ½.

In the magnetic tape, in a case where a maximum value of an absolute value of a difference between a servo band spacing obtained before storage, and a servo band spacing obtained after storage of N cycles, in a case where predetermined storage is set to one cycle, is defined as A, a medium life calculated by a linear function that is derived from the value of A and the value of the logarithm log.sub.eT of total storage time T of the storage of N cycles is 3 years or longer. The medium life is T in a case where the A satisfies Equation a: A=1.5−B. The B is calculated by multiplying a difference between a maximum value and a minimum value of the servo band spacings obtained in each of the five environments by ½.

In the magnetic tape, in a case where a maximum value of an absolute value of a difference between a servo band spacing obtained before storage in an environment of a temperature of 32° C. and relative humidity of 55% and a servo band spacing obtained after storage in the environment for a storage time T is set to A, and T is defined as 24 hours, 48 hours, 72 hours, 96 hours, or 120 hours, a medium life calculated by a linear function of A and a logarithm log.sub.eT of T, that are derived from a value of A and a value of the logarithm log.sub.eT of T obtained for each T is 3 years or longer. The medium life is T in a case where the A satisfies Equation 1: A=1.5−B.

In the magnetic tape, in a case where a maximum value of an absolute value of a difference between a servo band spacing obtained before storage in an environment of a temperature of 32° C. and relative humidity of 55% and a servo band spacing obtained after storage in the environment for a storage time T is set to A, and T is defined as 24 hours, 48 hours, 72 hours, 96 hours, or 120 hours, a medium life calculated by a linear function of A and a logarithm log.sub.eT of T, that are derived from a value of A and a value of the logarithm log.sub.eT of T obtained for each T is 3 years or longer. The medium life is T in a case where the A satisfies Equation 1: A=1.5−B.

An information processing device includes a recording unit that records a plurality of objects including data and metadata related to the data on a magnetic recording medium, and executes, after recording at least one of the objects, processing of recording first set data which is a set of the metadata included in the object. The first set data is the set of the metadata included in the object recorded after recording the first set data that is recorded immediately before. The magnetic recording medium has a magnetic layer containing a ferromagnetic powder and a binding agent on a non-magnetic support. A difference between spacings S.sub.0.5 and S.sub.13.5 measured under pressures of 0.5 atm and 13.5 atm by an optical interference method after n-hexane cleaning on a surface of the magnetic layer is equal to or less than 3.0 nm.