Abstract: Provided is an Al-containing hexagonal ferrite magnetic powder which produces an excellent durability-improving effect on a magnetic recording medium, wherein uniform pulverization of the magnetic powder can be easily achieved by dispersion treatment in preparation of a magnetic coating material even in cases where the magnetic powder has a small primary particle size or has a composition which is likely to produce hard secondary particles. The magnetic powder for a magnetic recording medium is an Al-containing hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, and has a particle size distribution in which the volume ratio of particles having a particle size of 30 ?m or more as measured by a laser diffraction particle size distribution analyzer with a dispersion pressure of 100 kPa is 5.0% or less, and an activation volume Vact of 1800 nm3 or less.

Abstract: A magnetic powder for a magnetic recording medium includes magnetic particles in which Ba in hexagonal barium ferrite is partially substituted with Sr, wherein a Dx volume represented by Dx volume (nm3) = Dxc × ? × (Dxa/2)2 is 2,200 nm3 or less, and an Sr/(Ba+Sr) molar ratio is 0.01 to 0.15. One that satisfies Ku ? 0.1 × [Sr/(Ba+Sr) molar ratio] + 0.13 is more preferred. For the formulas, Dxc is a crystallite diameter (nm) in a c-axis direction of a hexagonal ferrite crystal lattice, Dxa is a crystallite diameter (nm) in an a-axis direction of the same crystal lattice, ? is a circular constant, and Ku is a magnetocrystalline anisotropy constant (MJ/m3). By providing the hexagonal ferrite magnetic powder formed of fine particles, an effect of improving the perpendicular squareness ratio SQ of a magnetic recording medium is large.

Abstract: [Problem] A hexagonal barium ferrite magnetic powder formed of fine particles, wherein the anisotropic magnetic field distribution of a magnetic recording medium can be made to fall within a range effective in both improving the recording density and improving the SNR is provided. [Solution] A magnetic powder for a magnetic recording medium including magnetic particles in which Ba in hexagonal barium ferrite is partially substituted with Sr, wherein a Dx volume represented by the following formula (1) is 2,200 nm3 or less, an Sr/(Ba+Sr) molar ratio is 0.01 to 0.30, and an anisotropic magnetic field distribution is 1.00 or less. Dx volume (nm3)=Dxc×?×(Dxa/2)2??(1) Here, Dxc is a crystallite diameter (nm) in a c-axis direction of a hexagonal ferrite crystal lattice, Dxa is a crystallite diameter (nm) in an a-axis direction of the same crystal lattice, and n is a circular constant.

Abstract: The magnetic recording medium is used in a magnetic recording and reproducing device in which a reproduction bit size S is 40,000 nm2 or less, and a numerical value of a residual magnetic flux density Brvertical, which is expressed in a unit G, in a vertical direction of the magnetic recording medium is X or more. The X is a value calculated as X = -0.01S + 1550.

Abstract: Provided is a hexagonal ferrite magnetic powder for a magnetic recording medium, containing hexagonal ferrite magnetic particles having aluminum hydroxide adhered on the surface thereof, the hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, a Co/Fe molar ratio of 0.002 to 0.030, and a Nb/Fe molar ratio of 0.005 to 0.050, and having an Fe site valence AFe of 3.015 to 3.040 as calculated by AFe=(3+2×[Co/Fe]+5×[Nb/Fe])/(1+[Co/Fe]+[Nb/Fe]) wherein [Co/Fe] represents the Co/Fe molar ratio and [Nb/Fe] represents the Nb/Fe molar ratio, and preferably having an activation volume Vact of 1400 to 1800 nm3. This magnetic powder simultaneously achieves an increase in magnetic characteristics including SNR of a magnetic recording medium and a further increase in durability thereof.

Abstract: A test method of accurately evaluating wear resistance performance of a rubber material when used as a tread rubber of a tire, comprises the steps of: preparing a test piece of the rubber material having a ground contact surface extending in a circumferential direction; abrading the ground contact surface by rolling the test piece on a running surface of a wear testing machine at a slip ratio of not more than 3.5%; and evaluating the wear resistance performance of the test piece by comparing the amount of wear of the test piece with a predetermined threshold value.

Abstract: The magnetic tape has a magnetic layer containing ferromagnetic powder and binder on a nonmagnetic support, wherein the centerline average surface roughness Ra as measured on the surface on the magnetic layer side of the magnetic tape is less than or equal to 1.8 nm, and the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the magnetic layer side of the magnetic tape is less than or equal to 0.050.

Abstract: The magnetic recording medium includes a magnetic layer which contains ferromagnetic hexagonal ferrite powder and a binder, in which the magnetic layer contains an abrasive and a fatty acid ester, Int (110)/Int (114) of a crystal structure of the hexagonal ferrite, determined by performing XRD analysis on the magnetic layer by using an In-Plane method, is equal to or higher than 0.5 and equal to or lower than 4.0, a squareness ratio of the magnetic recording medium in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00, FWHMbefore and FWHMafter is greater than 0 nm and equal to or smaller than 7.0 nm, and a difference between spacings measured within a surface of the magnetic layer by an optical interference method before and after the heating in a vacuum is greater than 0 nm and equal to or smaller than 8.0 nm.

Abstract: The magnetic recording medium includes a non-magnetic support and a magnetic layer which contains ferromagnetic powder and a binder, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the magnetic layer contains an abrasive, Int (110)/Int (114) of a crystal structure of the hexagonal ferrite, determined by performing X-ray diffraction analysis on the magnetic layer by using an In-Plane method, to a peak intensity of a diffraction peak of (114) plane of the crystal structure is equal to or higher than 0.5 and equal to or lower than 4.0, a squareness ratio of the magnetic recording medium in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00, and a logarithmic decrement obtained by performing a pendulum viscoelasticity test on a surface of the magnetic layer is equal to or lower than 0.050.

Abstract: The magnetic tape includes a magnetic layer including ferromagnetic powder, non-magnetic powder, and a binding agent and a back coating layer including non-magnetic powder and a binding agent, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, a center line average surface roughness measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm, an intensity ratio of a peak intensity of a diffraction peak of a (110) plane with respect to a peak intensity of a diffraction peak of a (114) plane 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, and a contact angle with respect to 1-bromonaphthalene measured regarding a surface of the back coating layer is 15.0° to 30.0°.

Abstract: The magnetic tape includes a magnetic layer including ferromagnetic powder, non-magnetic powder, and a binding agent and a back coating layer including non-magnetic powder and a binding agent, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, an Ra measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm, an intensity ratio of a peak intensity of a diffraction peak of a (110) plane with respect to a peak intensity of a diffraction peak of a (114) plane 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, and a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding a surface of the back coating layer is equal to or smaller than 0.060.

Abstract: 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 XRD 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, full widths at half maximum of spacing distribution measured by optical interferometry regarding the surface of the back coating layer before and after performing a vacuum heating with respect to the magnetic tape are greater than 0 nm and equal to or smaller than 10.0 nm, and a difference between the spacings measured by optical interferometry regarding the surface of the back coating layer before and after performing the vacuum heating is greater than 0 nm and equal to or smaller than 8.0 nm.

Abstract: 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 C—H derived C concentration calculated from a C—H 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 %.

Abstract: The magnetic recording medium includes a non-magnetic support and a magnetic layer, wherein the magnetic layer contains ferromagnetic hexagonal ferrite powder and an abrasive, Int (110)/Int (114) of a crystal structure of the hexagonal ferrite determined by performing XRD analysis on the magnetic layer by using an In-Plane method is equal to or higher than 0.5 and equal to or lower than 4.0, a squareness ratio of the magnetic recording medium in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00, one or more kinds of components selected from the group consisting of a fatty acid and a fatty acid amide is contained in a magnetic layer side portion on the support, and a C—H-derived C concentration obtained by ESCA within a surface of the magnetic layer at a photoelectron take-off angle of 10° is equal to or higher than 45 at %.

Abstract: The magnetic recording medium includes a non-magnetic support and a magnetic layer containing ferromagnetic powder and a binder, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the magnetic layer contains an abrasive, an intensity ratio of a peak intensity of a diffraction peak of (110) plane of a crystal structure of the hexagonal ferrite, determined by performing X-ray diffraction analysis on the magnetic layer by using an In-Plane method, to a peak intensity of a diffraction peak of (114) plane of the crystal structure is equal to or higher than 0.5 and equal to or lower than 4.0, a squareness ratio of the magnetic recording medium in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00, and a contact angle with 1-bromonaphthalene measured within a surface of the magnetic layer is in a range of 50.0° to 55.0°.

Abstract: The magnetic recording medium has a non-magnetic support and a magnetic layer which is provided on the support and contains ferromagnetic powder and a binder, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the magnetic layer contains an abrasive, an intensity ratio (Int (110)/Int (114)) of a peak intensity Int (110) of a diffraction peak of (110) plane of a crystal structure of the hexagonal ferrite, determined by performing X-ray diffraction analysis on the magnetic layer by using an In-Plane method, to a peak intensity Int (114) of a diffraction peak of (114) plane of the crystal structure is equal to or higher than 0.5 and equal to or lower than 4.0, and a squareness ratio in a vertical direction is equal to or higher than 0.65 and equal to or lower than 1.00. The present invention also provides a method for manufacturing the magnetic recording medium.

Abstract: Provided is a hexagonal ferrite magnetic powder for a magnetic recording medium, containing hexagonal ferrite magnetic particles having aluminum hydroxide adhered on the surface thereof, the hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, a Co/Fe molar ratio of 0.002 to 0.030, and a Nb/Fe molar ratio of 0.005 to 0.050, and having an Fe site valence AFe of 3.015 to 3.040 as calculated by AFe=(3+2×[Co/Fe]+5×[Nb/Fe])/(1+[Co/Fe]+[Nb/Fe]) wherein [Co/Fe] represents the Co/Fe molar ratio and [Nb/Fe] represents the Nb/Fe molar ratio, and preferably having an activation volume Vact of 1400 to 1800 nm3. This magnetic powder simultaneously achieves an increase in magnetic characteristics including SNR of a magnetic recording medium and a further increase in durability thereof.