A non-magnetic substrate for a magnetic disk includes a substrate main body having two opposing main surfaces, and a metal film that is provided on the main surfaces and is made of a material having a loss factor of 0.01 or more. The non-magnetic substrate has a thickness (T+D) of 0.700 mm or less, the thickness (T+D) being the sum of a thickness T of the substrate main body and a thickness D of the metal film, and a ratio D/T of the thickness D of the metal film to the thickness T of the substrate main body is 0.025 or more.

There is provided a magnetic recording medium of which an average thickness t.sub.T is t.sub.T5.6 m, a dimensional change amount w in a width direction with respect to a change in tension in a longitudinal direction is 660 ppm/Nw, a squareness ratio in a vertical direction is 65% or more, and a width deformation coefficient b during long-term storage in a case where a long-term storage width change amount Y is defined as Y=blog(t) is 0.06 mb0.06 m.

A magnetic recording medium is provided and includes a magnetic layer, a non-magnetic layer, a base layer and a back layer, wherein an average thickness t.sub.T of the magnetic recording medium is t.sub.T5.3 m, a dimensional change amount w in a width direction with respect to a change in tension in a longitudinal direction is 700 ppm/Nw, a thickness of the non-magnetic layer is 2.0 m or less, a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more, and the magnetic layer includes a magnetic powder.

Disclosed is a perpendicularly magnetized film structure using a highly heat resistant underlayer film on which a cubic or tetragonal perpendicularly magnetized film can grow, comprising a substrate of a cubic single crystal substrate having a (001) plane or a substrate having a cubic oriented film that grows to have the (001) plane; an underlayer formed on the substrate from a thin film of a metal having an hcp structure in which the [0001] direction of the thin metal film forms an angle in the range of 42 to 54 with respect to the <001> direction or the (001) orientation of the substrate; and a perpendicularly magnetized layer located on the metal underlayer and formed from a cubic material selected from a Co-based Heusler alloy and a cobalt-iron (CoFe) alloy having a bcc structure a constituent material, and grown to have the (001) plane.

There is provided a magnetic recording medium of which an average thickness t.sub.T is t.sub.T5.6 , a dimensional change amount w in a width direction with respect to a change in tension in a longitudinal direction is 660 ppm/Nw, a squareness ratio in a vertical direction is 65% or more, and a width deformation coefficient b during long-term storage in a case where a long-term storage width change amount Y is defined as Y=blog(t) is 0.06 mb0.06 .

A magnetic recording medium is provided and includes a magnetic layer, a non-magnetic layer, a base layer and a back layer, wherein an average thickness t.sub.T of the magnetic recording medium is t.sub.T5.3 m, a dimensional change amount w in a width direction with respect to a change in tension in a longitudinal direction is 700 ppm/Nw, a thickness of the non-magnetic layer is 2.0 m or less, a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more, and the magnetic layer includes a magnetic powder.

A method of encoding information in an object that may allow for enhanced tailorability of the encoding during the processing and/or also enhance the amount of information encoded in the object. More particularly, the method of encoding the object enables the magnetic characteristics at different spatial locations of the object to be modified to form a spatial array of the different magnetic characteristics for representing the encoded information. The method can be used to permanently embed a magnetic signature in a non-magnetic object, for example. More specifically, the method allows different portions of the object to exhibit different magnetic characteristics at each spatial location of the object in three dimensions, and more particularly configuring the magnetic vectors of those portions in many possible orientations with a 4n steradian solid angle and/or with different intensities.

An object of the present invention is to provide a magnetic recording medium, which contains -type iron oxide particles and has excellent SNR, a manufacturing method of -type iron oxide particles, and a manufacturing method of a magnetic recording medium.

The object is achieved by a magnetic recording medium containing -type iron oxide particles, in which a coefficient of variation of an aspect ratio of the -type iron oxide particles is equal to or smaller than 18%, and a squareness ratio of the magnetic recording medium measured in a longitudinal direction of the magnetic recording medium is higher than 0.3 and equal to or lower than 0.5. The object is also achieved by the application of the magnetic recording medium.

A heat-assisted magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L1.sub.0 crystal structure and first and second layers, arranged in this order. Each of the first and second layers has a granular structure including C, SiO.sub.2, and BN at grain boundaries. Vol % of the grain boundaries in each of the first and second layers is 25 to 45 vol %. Vol % of C in the first layer is 5 to 22 vol %, and a volume ratio of SiO.sub.2 with respect to BN in each of the first and second layers is 0.25 to 3.5. Vol % of SiO.sub.2 in the second layer is greater than that of the first layer by 5 vol % or more. Vol % of BN in the second layer is smaller than that in the first layer by 2 vol % or more.

A heat-assisted magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L1.sub.0 crystal structure and first and second layers, arranged in this order. Each of the first and second layers has a granular structure including C, SiO.sub.2, and BN at grain boundaries. Vol % of the grain boundaries in each of the first and second layers is 25 to 45 vol %. Vol % of C in the first layer is 5 to 22 vol %, and a volume ratio of SiO.sub.2 with respect to BN in each of the first and second layers is 0.25 to 3.5. Vol % of SiO.sub.2 in the second layer is greater than that of the first layer by 5 vol % or more. Vol % of BN in the second layer is smaller than that in the first layer by 2 vol % or more.