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 0.04 m to 0.08 m, and an absolute value N 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.

The curing agent for a magnetic recording medium includes a compound represented by General Formula 1. In General Formula 1, X represents a monovalent heterocyclic group or a monovalent group represented by General Formula 2, Z represents an m-valent organic group, and m represents an integer of 2 or more. In General Formula 2, R.sup.1 represents an alkyl group, R.sup.2 represents a hydrogen atom, an alkyl group, or an aryl group, and * represents a bonding site with an adjacent carbon atom.

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Provided are a magnetic tape including: a non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, in which a total thickness of the magnetic tape is equal to or smaller than 5.30 m, the magnetic layer has a servo pattern, a center line average surface roughness Ra measured on a surface of the magnetic layer is equal to or smaller than 1.8 nm, and an absolute value N of a difference between a refractive index Nxy of the magnetic layer, measured in an in-plane direction and a refractive index Nz of the magnetic layer, measured in a thickness direction is 0.25 to 0.40, a magnetic tape cartridge and a magnetic tape apparatus including this magnetic tape, a magnetic tape cartridge and a magnetic tape apparatus including this magnetic tape.

Provided are a magnetic tape including: a non-magnetic support; a magnetic layer including ferromagnetic powder and a binding agent on one surface side of the non-magnetic support; and a back coating layer including non-magnetic powder and a binding agent on the other surface side of the non-magnetic support, in which an isoelectric point of a surface zeta potential of the magnetic layer is equal to or greater than 5.5, and an isoelectric point of a surface zeta potential of the back coating layer is equal to or greater than 4.5, a magnetic tape cartridge, and a magnetic tape apparatus including this magnetic tape.

The average thickness t.sub.T of a magnetic recording medium meets the requirement that t.sub.T 5.5 [m], and the dimensional change amount w in the width direction of the magnetic recording medium with respect to the tension change in the longitudinal direction of the magnetic recording medium meets the requirement that 700 ppm/Nw.

The magnetic tape includes: a non-magnetic support; and a magnetic layer containing a ferromagnetic powder, in which an arithmetic average roughness Ra measured on a surface of the magnetic layer is 1.5 nm or less, and standard deviation a of the Ra in a width direction of the surface of the magnetic layer is 0.20 nm or less.

The magnetic tape has a magnetic layer and a backcoat layer. The Ra on the magnetic layer side surface is less than or equal to 1.8 nm, the coefficient of friction measured on the base portion of the magnetic layer side surface is less than or equal to 0.35, and the Ra measured on the backcoat layer side surface is less than or equal to 5.0 nm. The backcoat layer contains a fatty acid ester. In addition, the FWHM.sub.before measured on the backcoat layer side surface before vacuum heating is greater than 0 nm but less than or equal to 10.0 nm, the FWHM.sub.after after vacuum heating is greater than 0 nm but less than or equal to 10.0 nm, and the difference between the spacing measured on the backcoat layer side surface after and before vacuum heating is greater than 0 nm but less than or equal to 8.0 nm.

The magnetic tape cartridge group includes a plurality of magnetic tape cartridges. Regarding 100 reels of magnetic tape cartridges, in a case where a maximum value of an absolute value of a difference between a servo band spacing obtained before predetermined storage and a servo band spacing obtained after the predetermined storage is defined as A, an arithmetic mean of medium lives calculated by a linear function derived from a value of A obtained for different N and a value of the logarithm of total storage time T of the storage of N cycles is 3 years or longer and 3? is 1 year or shorter. Medium life: T in a case where A satisfies A=1.5?B. B: a value calculated by multiplying a difference between a maximum value and a minimum value of servo band spacings obtained in each of the five environments by ?.

The magnetic tape includes a non-magnetic support; a magnetic layer including a ferromagnetic powder and a binding agent on one surface of the non-magnetic support; and a back coating layer including a non-magnetic powder and a binding agent on the other surface of the non-magnetic support, in which a center line average surface roughness Ra measured regarding a surface of the back coating layer is equal to or smaller than 7.0 nm, and a difference between a spacing S.sub.after measured by optical interferometry regarding the surface of the back coating layer after methyl ethyl ketone cleaning and a spacing S.sub.before measured by optical interferometry regarding the surface of the back coating layer before methyl ethyl ketone cleaning is greater than 0 nm and equal to or smaller than 30.0 nm.

Provided is a magnetic tape in which an Ra measured regarding a surface of a magnetic layer is equal to or smaller than 1.8 nm, Int(110)/Int(114) of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0, a vertical squareness ratio of the magnetic tape is 0.65 to 1.00, the back coating layer includes one or more kinds of component selected from the group consisting of fatty acid and fatty acid amide, and a CH derived C concentration calculated from a CH peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed on the surface of the back coating layer at a photoelectron take-off angle of 10 degrees is equal to or greater than 35 atom %.