Provided is an electromagnetic-wave absorber composition and an electromagnetic-wave absorber that can favorably absorb a plurality of electromagnetic waves of different frequencies in a high frequency band in or above the millimeter-wave band. The electromagnetic-wave absorber composition includes a magnetic iron oxide that magnetically resonates at a high frequency in or above the millimeter-wave band and a resin binder. The electromagnetic-wave absorber composition has two or more extrema separated from each other on a differential curve obtained by differentiating a magnetic property hysteresis loop at an applied magnetic field intensity of from 16 kOe to −16 kOe. The electromagnetic-wave absorber includes an electromagnetic-wave absorbing layer formed of the above-described electromagnetic-wave absorber composition.

A magnetic fiber comprises a core comprising a spinel ferrite of formula Me.sub.1-xM.sub.xFe.sub.yO.sub.4, wherein Me is Mg, Mn, Fe, Co, Ni, Cu, Zn, or a combination thereof, x=0 to 0.25, and y=1.5 to 2.5, wherein the core is solid or at least partially hollow; and a shell at least partially surrounding the core, and comprising a Me.sub.1-xM.sub.xFe.sub.y alloy, wherein when the core is solid with Me=Ni and x=0 the magnetic fiber has a diameter of greater than 0.3 micrometer. A magneto-dielectric material having a magnetic loss tangent of less than or equal to 0.03 at 1 GHz comprises a polymer matrix; and a plurality of the magnetic fibers.

The disclosed technology relates to a ceramic composition and an article formed therefrom. A ceramic article for radio frequency applications is formed of a ceramic material having a chemical formula represented by: Bi.sub.1.0+aY.sub.2.0-a-x-2yCa.sub.x+2yFe.sub.5-x-yM.sup.IV.sub.xV.sub.yO.sub.12 or Bi.sub.1.0+aY.sub.2.0-a-2yCa.sub.2yFe.sub.5-y-zV.sub.yIn.sub.zO.sub.12. The ceramic material has a composition such that a normalized change in saturation magnetization (Δ4πMs), defined as Δ4πMs=[(4πMs at 20° C.)-(4πMs at 120° C.)]/(4πMs at 20° C.), is less than about 0.35.

When manufacturing a magnetic body which is made of a ferrite material containing Fe, Ni, and Zn, and whose Mn content is 0.1288 percent by mass or higher, or a magnetic body which is made of a ferrite material containing Fe, Ni, Zn, and Cu, and whose Mn content is 0.1178 percent by mass or higher, an iron oxide powder whose Mn content is 0.20 percent by mass or higher is used as a raw material powder.

A method for manufacturing a ferrite sheet is provided. A method for manufacturing a ferrite sheet comprises the steps of: preparing a ferrite block body having a shape of a cylindrical or polygonal column; and cutting the ferrite block body to be separated into plate-shaped sheets having a predetermined thickness.

When manufacturing a magnetic body whose primary component is Ni—Zn ferrite, an iron oxide powder whose Mn content is 0.20 to 0.85 percent by mass is used as a raw material powder, or, in addition to using an iron oxide powder whose Mn content is 0.20 percent by mass or higher as a raw material powder, a mol ratio of Ni to Zn (Ni/Zn) in the ferrite material is determined based on the Mn content in the iron oxide powder and the raw material powders are compounded in such a way that the mol ratio is achieved. The magnetic body does not contain any additives as essential components other than the primary components of the Ni—Zn ferrite material. A coil component using the magnetic body has excellent direct-current superimposition property and magnetic permeability.

Provided are a ferrite powder capable of maintaining a high withstand voltage even when used in a resin composition having high magnetic properties and electrical resistivity and a high filling ratio, and a method for producing the same. A ferrite powder composed of spherical ferrite particles, wherein the ferrite powder contains iron (Fe): 55.0-70.0 mass % and manganese (Mn): 3.5-18.5 mass %, the ferrite powder containing more than 0.0 mass % to 7.5 mass % α-Fe.sub.2O.sub.3, and the ferrite powder has a volume average particle size (D50) of 15.0 μm or less.

A ceramic composition contains Fe, Cu, Ni, Zn, Co, and Cr. When Fe, Cu, Ni, and Zn are converted to Fe.sub.2O.sub.3, CuO, NiO, and ZnO, respectively, and when a total amount of Fe.sub.2O.sub.3, CuO, NiO, and ZnO is 100 parts by mole, the ceramic composition contains 45.00 to 49.70 parts by mole Fe in terms of Fe.sub.2O.sub.3, 2.00 to 8.00 parts by mole Cu in terms of CuO, 19.40 to 45.40 parts by mole Ni in terms of NiO, and 1.00 to 27.00 parts by mole Zn in terms of ZnO. When Fe, Cu, Ni, and Zn are converted to Fe.sub.2O.sub.3, CuO, NiO, and ZnO, respectively, and when a total amount of Fe.sub.2O.sub.3, CuO, NiO, and ZnO is 100 parts by weight, the ceramic composition contains 5 to 100 ppm Co in terms of CoO and 10 to 400 ppm Cr in terms of Cr.sub.2O.sub.3.

A ceramic composition contains Fe, Cu, Ni, Zn, Co, and Cr. When Fe, Cu, Ni, and Zn are converted to Fe.sub.2O.sub.3, CuO, NiO, and ZnO, respectively, and a total amount of Fe.sub.2O.sub.3, CuO, NiO, and ZnO is 100 parts by mole, the ceramic composition contains from 48.20 to 49.85 parts by mole Fe in terms of Fe.sub.2O.sub.3, from 2.00 parts to 8.00 parts by mole Cu in terms of CuO, from 11.90 to 18.70 parts by mole Ni in terms of NiO, and from 27.00 to 33.50 parts by mole Zn in terms of ZnO. When Fe, Cu, Ni, and Zn are converted to Fe.sub.2O.sub.3, CuO, NiO, and ZnO, respectively, and a total amount of Fe.sub.2O.sub.3, CuO, NiO, and ZnO is 100 parts by weight, the ceramic composition contains from 5 to 100 ppm Co in terms of CoO and from 10 to 400 ppm in terms of Cr.sub.2O.sub.3.

An inductor core includes a tubular shaped or pillar shaped magnetic main body comprising a magnetic material. The magnetic main body includes: an inclined portion including an inclined surface with an outer circumferential surface of a truncated cone having an outer diameter increasing from one end of the magnetic main body toward the other end; and a straight body portion that is coaxial with the inclined portion and extends from the other end toward the one end, the straight body portion being connected to the inclined portion and including an outer peripheral surface with an outer circumferential surface of a circle tubular body or a cylindrical column body. A skewness Rsk of an outer peripheral surface of the straight body portion located near the inclined portion is smaller than a skewness Rsk of an outer peripheral surface of the straight body portion located near the other end.