A magnetic recording medium includes a layer structure including a magnetic layer, a non-magnetic layer, and a base layer in this order, in which an average thickness t.sub.T is t.sub.T5.5 m, a dimensional variation w in a width direction to tension change in a longitudinal direction is 660 ppm/Nw, and an average thickness t.sub.n of the non-magnetic layer is t.sub.n1.0 m.

A magnetic recording medium includes: an elongated substrate having flexibility; a first layer, being provided on the substrate, containing Cr, Ni, and Fe, and having a face-centered cubic lattice structure with a (111) plane preferentially oriented so as to be parallel to a surface of the substrate; a second layer, being provided on the first layer, containing Co and O, having a ratio of an average atomic concentration of O to an average atomic concentration of Co of 1 or more, and having a column structure with an average particle diameter of 3 nm or more and 13 nm or less; a third layer, being provided on the second layer, and containing Ru; and a perpendicular recording layer, being provided on the third layer.

A magnetic recording medium includes: an elongated substrate having flexibility; a first layer, being provided on the substrate, containing Cr, Ni, and Fe, and having a face-centered cubic lattice structure with a (111) plane preferentially oriented so as to be parallel to a surface of the substrate; a second layer, being provided on the first layer, containing Co and O, having a ratio of an average atomic concentration of O to an average atomic concentration of Co of 1 or more, and having a column structure with an average particle diameter of 3 nm or more and 13 nm or less; a third layer, being provided on the second layer, and containing Ru; and a perpendicular recording layer, being provided on the third layer.

A magnetic head includes a main magnetic pole, a write shield separated from the main magnetic pole by a write gap, a first side shield that is separated from the main magnetic pole by a first side gap, a second side shield that is separated from the main magnetic pole by a second side gap, a first layer that has a first magnetic relative permeability and is disposed in the write gap between the main magnetic pole and the write shield, and a second layer that has a second magnetic relative permeability and is disposed in the first side gap and the second side gap, wherein the first magnetic relative permeability is smaller than the second magnetic relative permeability.

A magnetic head includes a main magnetic pole, a write shield separated from the main magnetic pole by a write gap, a first side shield that is separated from the main magnetic pole by a first side gap, a second side shield that is separated from the main magnetic pole by a second side gap, a first layer that has a first magnetic relative permeability and is disposed in the write gap between the main magnetic pole and the write shield, and a second layer that has a second magnetic relative permeability and is disposed in the first side gap and the second side gap, wherein the first magnetic relative permeability is smaller than the second magnetic relative permeability.

A magnetic recording cartridge is provided and including a magnetic recording medium, wherein an average thickness of the magnetic recording medium t.sub.T is 3.5 mt.sub.T5.6 m, a dimensional change amount w in a width direction of the magnetic recording medium with respect to a tension change in a longitudinal direction of the magnetic recording medium is 700 ppm/Nw20000 ppm, and the magnetic recording medium is accommodated in a state of being wound around the reel in the cartridge case and (a servo track width on an inner side of winding of the magnetic recording medium)(a servo track width on an outer side of winding of the magnetic recording medium)>0 is satisfied.

A sputtering target material, wherein the strength of a sputtering target material can be enhanced without using pure Ta to prevent cracking during sputtering and generating particles and to suppress an irregular composition of a sputtered film, is provided. The present invention provides a sputtering target material containing, in at %, 35% to 50% of Ta with the balance being Ni and an inevitable impurity, wherein the sputtering target is composed only of a Ni.sub.2Ta compound phase and a NiTa compound phase, and a microstructure in each of the Ni.sub.2Ta compound phase and the NiTa compound phase has a maximum inscribed circle diameter of not more than 10 m.

A magnetic head includes a main magnetic pole, a write shield separated from the main magnetic pole by a write gap, a first side shield that is separated from the main magnetic pole by a first side gap, a second side shield that is separated from the main magnetic pole by a second side gap, a first layer that has a first magnetic relative permeability and is disposed in the write gap between the main magnetic pole and the write shield, and a second layer that has a second magnetic relative permeability and is disposed in the first side gap and the second side gap, wherein the first magnetic relative permeability is smaller than the second magnetic relative permeability.

A magnetic head includes a main magnetic pole, a write shield separated from the main magnetic pole by a write gap, a first side shield that is separated from the main magnetic pole by a first side gap, a second side shield that is separated from the main magnetic pole by a second side gap, a first layer that has a first magnetic relative permeability and is disposed in the write gap between the main magnetic pole and the write shield, and a second layer that has a second magnetic relative permeability and is disposed in the first side gap and the second side gap, wherein the first magnetic relative permeability is smaller than the second magnetic relative permeability.

An apparatus includes a first magnetic layer. A second magnetic layer overlies the first magnetic layer and is magnetically softer than the first magnetic layer. An exchange control layer is between the first magnetic layer and the second magnetic layer. The includes a higher Ms (saturation magnetization) than the first magnetic layer at room temperature.