According to one aspect of the present invention, an organic fluorine compound is represented by a general formula
(R-π-E-CH.sub.2-A-CH.sub.2-E′).sub.n-π′-G  (1B) (where n is an integer of 2 to 5, A is a divalent perfluoropolyether group, π is an arylene group or a single bond, R is an alkenyl group or an alkynyl group, and E and E′ are each independently an ether bond or an ester bond or a group that is represented by a chemical formula
—O—CH.sub.2CH(OH)CH.sub.2O—
π′ is a group in which n+1 hydrogen atoms are separated from benzene, G is an organic group containing a fullerene skeleton, the n number of groups each of which is represented by a general formula
R-π-E-CH.sub.2-A-CH.sub.2-E′-
may be the same or different, and at least one π among the n number of π is an arylene group).

According to one aspect of the present invention, an organic fluorine compound is represented by a general formula
(R-π-E-CH.sub.2-A-CH.sub.2-E′).sub.n-π′-G  (1B) (where n is an integer of 2 to 5, A is a divalent perfluoropolyether group, π is an arylene group or a single bond, R is an alkenyl group or an alkynyl group, and E and E′ are each independently an ether bond or an ester bond or a group that is represented by a chemical formula
—O—CH.sub.2CH(OH)CH.sub.2O—
π′ is a group in which n+1 hydrogen atoms are separated from benzene, G is an organic group containing a fullerene skeleton, the n number of groups each of which is represented by a general formula
R-π-E-CH.sub.2-A-CH.sub.2-E′-
may be the same or different, and at least one π among the n number of π is an arylene group).

A magnetic property measuring apparatus measures magnetic properties of a magnetic recording medium, and includes a rotating mechanism which rotates the magnetic recording medium, a heating or cooling mechanism which heats or cools the magnetic recording medium; a temperature measuring mechanism which measures a temperature of the magnetic recording medium, a laser heating mechanism, disposed opposite to a measurement site of the magnetic recording medium, which heats the measurement site without making contact with the measurement site, a magnetic write part, disposed opposite to the measurement site, which magnetizes the measurement site without making contact with the measurement site, and a magnetic read part, disposed opposite to the measurement site, which reads a magnetic flux leakage at the measurement site without making contact with the measurement site.

A lubricant for a magnetic recording medium capable of forming a lubricant layer having excellent adhesion to a protective layer is provided. A lubricant for a magnetic recording medium contains a fluorine-containing ether compound in which a group having an ethylenic carbon-carbon double bond is disposed at one or both terminals of a perfluoroalkyl polyether chain. It is preferable that the group having the ethylenic carbon-carbon double bond is disposed at one terminal of the perfluoroalkyl polyether chain, and a hydroxyl group is disposed at other terminal. It is preferable that the lubricant for a magnetic recording medium contains a compound in which one or more functional groups selected from a hydroxyl group, an amino group, an amido group and a carboxyl group is disposed at one or both terminals of a perfluoroalkyl polyether chain.

Provided is a sputtering target containing 0.05 at % or more of Bi, and having a total content of metal oxides of from 10 vol % to 70 vol %, the balance containing at least Ru.

Various apparatuses, systems, methods, and media are disclosed to provide a magnetic recording medium with a tungsten (W) pre-seed layer. The W pre-seed layer has a higher conductance than a CrTi pre-seed layer with a similar thickness. In one embodiment, the W pre-seed layer is made of about 95 atomic percent or more of W. The W pre-seed layer has lower electrical resistivity than the CrTi pre-seed layer. As a result, the thickness of the W pre-seed layer can be reduced as compared to the thickness of a CrTi pre-seed layer if a similar conductance is to be achieved. The magnetic recording materials deposited on top of the W pre-seed layer with the reduced thickness provide comparable crystallographic orientation and recording performance to those deposited on top of a thicker CrTi pre-seed layer with a similar conductance.

According to an embodiment, a manufacturing method includes: estimating a distribution of an initial value of a clearance of a magnetic head on a first recording surface; and recording first spiral signals on the first recording surface while controlling a clearance using the distribution of the initial value of the estimated clearance. The manufacturing method includes measuring a distribution of an initial value of a clearance of a magnetic head on a second recording surface under positioning control using the first spiral signals recorded on the first recording surface. The manufacturing method includes recording the first spiral signals on the second recording surface while controlling a clearance using the distribution of the initial value of the measured clearance of the magnetic head on the second recording surface. The manufacturing method includes recording the second spiral signals on a third recording surface under positioning control using the first spiral signals recorded on the second recording surface.

According to an embodiment, a manufacturing method includes: estimating a distribution of an initial value of a clearance of a magnetic head on a first recording surface; and recording first spiral signals on the first recording surface while controlling a clearance using the distribution of the initial value of the estimated clearance. The manufacturing method includes measuring a distribution of an initial value of a clearance of a magnetic head on a second recording surface under positioning control using the first spiral signals recorded on the first recording surface. The manufacturing method includes recording the first spiral signals on the second recording surface while controlling a clearance using the distribution of the initial value of the measured clearance of the magnetic head on the second recording surface. The manufacturing method includes recording the second spiral signals on a third recording surface under positioning control using the first spiral signals recorded on the second recording surface.

The present invention provides a glass composition having a low density and having a specific elastic modulus high enough to reduce deflection. The glass composition includes, as components, in mol %: 60 to 75% SiO.sub.2; 5 to 15% Al.sub.2O.sub.3; 0.5 to 5% MgO; 0.5 to 10% CaO; 5 to 20% Li.sub.2O; 2 to 10% Na.sub.2O; and 0 to 5% K.sub.2O, and has a density of 2.48 g/cm.sup.3 or less. The glass composition has a specific elastic modulus of, for example, 33.5×10.sup.6 Nm/kg or more.

An aluminum alloy substrate for a magnetic disk including an aluminum alloy containing 0.1 to 3.0 mass % of Fe, 0.005 to 1.000 mass % of Cu, and 0.005 to 1.000 mass % of Zn, with a balance of Al and inevitable impurities, wherein in an outer peripheral surface thereof, the number of holes having maximum diameters of 10 μm or more is 200/mm.sup.2 or less, an aluminum alloy base disk for a magnetic disk and a magnetic disk, using the aluminum alloy substrate, and methods for manufacturing these.