Abstract: The magnetic recording medium includes a non-magnetic support; and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, in which the magnetic layer further includes a compound including one or more partial structures selected from the group consisting of a partial structure represented by Formula 1 and a partial structure represented by Formula 2, and a polyalkyleneimine chain. A magnetic recording and reproducing apparatus including this magnetic recording medium. A composition for a magnetic recording medium including a ferromagnetic powder and the compound. L1 in Formula 1 and L2 in Formula 2 each independently represent a divalent linking group, Z1 in Formula 1 and Z2 in Formula 2 each independently represent a monovalent group represented by —OM or a monovalent group represented by —O?A+, M represents a hydrogen atom or an alkali metal atom, and A+ represents an ammonium cation.

Abstract: Disclosed are a particle of a 13-iron oxyhydroxide-based compound represented by Formula (1), in which an average equivalent circle diameter of primary particles is 5 nm to 30 nm, and a coefficient of variation of equivalent circle diameters of the primary particles is 10% to 30% [In Formula (1), A represents at least one kind of metal element other than Fe, and a represents a number that satisfies a relationship of 0?a<1.], and applications thereof.

Abstract: Provided is a ferromagnetic powder for magnetic recording, in which an activation volume is 800 nm3 to 1,500 nm3, an average plate ratio is 2.0 to 5.0, a rare earth atom content is 0.5 atom % to 5.0 atom %, and an aluminum atom content is greater than 10.0 atom % and equal to or smaller than 20.0 atom %, with respect to 100 atom % of iron atom, and the ferromagnetic powder is a plate-shaped hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution and an aluminum atom surface layer portion uneven distribution, and a magnetic recording medium including this ferromagnetic powder for magnetic recording in a magnetic layer.

Abstract: Hexagonal ferrite powder has an average particle size falling within a range of 10 nm to 50 nm, a switching field distribution SFD23° C. measured at a temperature of 23° C. that is less than or equal to 0.80, and a ratio of a switching field distribution SFD?190° C. that is measured at a temperature of ?190° C. to the SFD23° C. (SFD?190° C./SFD23° C.) that is greater than 0.80.

Abstract: The invention provides a core-shell particle which can provide, by being calcinated, epsilon type iron oxide-based compound particles that have a small coefficient of variation of primary particle diameter and show excellent SNR and running durability when employed in a magnetic recording medium as well as applications thereof. The core-shell particle includes: a core including at least one iron oxide selected from Fe2O3 or Fe3O4, or iron oxyhydroxide; and a shell that coats the core, the shell including a polycondensate of a metal alkoxide and a metal element other than iron, as well as applications thereof.

Abstract: Provided is hexagonal strontium ferrite powder for magnetic recording, in which an activation volume is 800 to 1,500 nm3, a content of rare earth atom with respect to 100 atom % of iron atom is 0.5 to 5.0 atom %, and a rare earth atom surface portion uneven distribution is provided.

Abstract: Provided is a magnetic recording medium including: a non-magnetic support; and a magnetic layer including particles of at least one kind of epsilon type iron oxide-based compound selected from the group consisting of ?-Fe2O3 and a compound represented by Formula (1), and a binding agent, at least on one surface of the non-magnetic support, in which an average area Sdc of a magnetic cluster in a DC demagnetization state measured with a magnetic force microscope satisfies a relationship of 500 nm2<Sdc<3,000 nm2, and coercivity Hc satisfies a relationship of 319 kA/m<Hc<957 kA/m. In Formula (1), A represents at least one kind of metal element other than Fe and a satisfies a relationship of 0<a<2.

Abstract: Provided is a magnetic recording medium including: a non-magnetic support; and a magnetic layer including particles of at least one kind of epsilon type iron oxide-based compound selected from the group consisting of ?-Fe2O3 and a compound represented by Formula (1), an abrasive, and a binding agent, at least on one surface of the non-magnetic support, in which an average equivalent circle diameter of the particles of the epsilon type iron oxide-based compound is 7 nm to 18 nm, an average equivalent circle diameter of the abrasive in a plan view of the magnetic layer is 20 nm to 1,000 nm, and a coefficient of variation of the equivalent circle diameter of the abrasive is 30% to 60%. In Formula (1), A represents at least one kind of metal element other than Fe and a satisfies a relationship of 0<a<2.

Abstract: A core-shell particle includes: a core including an iron oxyhydroxide compound represented by Formula A3a3Fe1?a3OOH (in which A3 represents at least one metal element other than Fe, and a3 satisfies 0<a3<1) or at least one iron oxide compound selected from the group consisting of Fe2O3, a compound represented by Formula A1a1Fe2?a1O3 (in which A1 represents at least one metal element other than Fe, and a1 satisfies 0<a1<2), Fe3O4, and a compound represented by Formula A2a2Fe3?a2O4 (in which A2 represents at least one metal element other than Fe, and a2 satisfies 0<a2<2); and a shell which covers the core and includes a polycondensate of a metal alkoxide.

Abstract: A magnetic recording medium includes: a non-magnetic support; and a magnetic layer including a binding agent and a ferromagnetic powder including at least one epsilon-type iron oxide compound selected from the group consisting of ?-Fe2O3 and compound represented by Formula (1) (A represents at least one metal element other than Fe, and a satisfies 0<a<2), in which a value of magnetic field Hc with respect to magnetic field Hc? is from 0.6 to 1.0, and Hc? satisfies Expression (II): 119 kA/m<Hc?<2380 kA/m. The magnetic field Hc? is a magnetic field when the value of Expression (I): d2M/dH2 is zero, wherein a magnetization M, which is obtained by a magnetic field-magnetization curve obtained by measurement under specific conditions, is subjected to second derivative with respect to an applied magnetic field H, and magnetic field Hc is a magnetic field when the magnetization is zero in the curve.

Abstract: An aspect of the present invention relates to A method of manufacturing hexagonal ferrite powder, which comprises heating to equal to or higher than 300° C. and pressurizing to equal to or higher than 20 MPa a hexagonal ferrite precursor-containing water-based solution, to convert the precursor to hexagonal ferrite, wherein the water-based solution comprises at least a reducing compound selected from the group consisting of a reducing inorganic compound and a reducing organic compound that have a reducing property and exist as a solid or a liquid at ordinary temperature and ordinary pressure, as well as, when the reducing compound is a reducing inorganic compound, the water-based solution further comprises an organic compound.

Abstract: Provided is an ?-iron oxide type ferromagnetic powder with a ratio Hc173K/Hc296K between a coercive force Hc173K measured at a temperature of 173 K and a coercive force Hc296K measured at a temperature of 296 K is higher than 1.00 and less than 2.00, and a magnetic recording medium containing the ?-iron oxide type ferromagnetic powder in a magnetic layer.

Abstract: The method of manufacturing hexagonal ferrite powder includes preparing a hexagonal ferrite precursor by mixing an iron salt and a divalent metal salt in a water-based solution, and converting the hexagonal ferrite precursor into hexagonal ferrite within a reaction flow passage, within which a fluid flowing therein is subjected to heating and pressurizing, by continuously feeding a water-based solution containing the hexagonal ferrite precursor and gelatin to the reaction flow passage.

Abstract: The hexagonal ferrite powder has an activation volume of greater than or equal to 800 nm3 but less than 1,200 nm3, a rare earth atom content falling within a range of 0.5 to 8.0 atom % per 100 atom % of iron atoms, and a localized presence of rare earth atoms in the surface layer portion, as well as is in the form of ellipsoidal powder.

Abstract: A production method for metal oxide particles includes: obtaining precursor particles of a metal oxide by performing a synthesis reaction of the precursor particles in the presence of an organic compound; and converting the obtained precursor particles into metal oxide particles by heating an aqueous solution containing the precursor particles to 300° C. or higher and pressurizing the aqueous solution at a pressure of 20 MPa or higher.

Abstract: Hexagonal ferrite powder has an average particle size falling within a range of 10 nm to 50 nm, a switching field distribution SFD23° C. measured at a temperature of 23° C. that is less than or equal to 0.80, and a ratio of a switching field distribution SFD?190° C. that is measured at a temperature of ?190° C. to the SFD23° C. (SFD?190° C./SFD23° C.) that is greater than 0.80.

Abstract: An aspect of the present invention relates to a magnetic recording medium, which comprises magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the ferromagnetic hexagonal ferrite powder has an activation volume ranging from 800 nm3 to 1,300 nm3, and 1 percent to 50 percent of particles constituting the ferromagnetic hexagonal ferrite powder are ferromagnetic hexagonal ferrite particles, each of which has an indentation with a depth of equal to or more than 1/10 of an equivalent projected circle diameter of the ferromagnetic hexagonal ferrite particle.

Abstract: Provided are hexagonal ferrite magnetic powder for magnetic recording, being comprised of hexagonal ferrite magnetic particles having a crystalline metal oxide adhered to a surface thereof, a method for producing hexagonal ferrite magnetic particles having a crystalline metal oxide adhered to a surface thereof, and a magnetic recording medium.

Abstract: An aspect of the present invention relates to magnetic powder, which is magnetoplumbite hexagonal strontium ferrite magnetic powder comprising 0.05 atomic percent to 3 atomic percent of Ca per 100 atomic percent of Fe, but comprising no rare earth elements or transition metal elements other than Fe, the average particle size of which ranges from 10 nm to 25 nm, and which is magnetic powder for magnetic recording.

Abstract: An aspect of the present invention relates to magnetic powder, which is magnetoplumbite hexagonal strontium ferrite magnetic powder comprising 1 atomic percent to 5 atomic percent of Ba per 100 atomic percent of Fe, the average particle size of which ranges from 10 nm to 25 nm, and which is magnetic powder for magnetic recording.