To provide a transmission-type electromagnetic-wave absorber that can satisfactorily absorb electromagnetic waves of high frequencies in or above the millimeter-wave band while reducing the reflection of electromagnetic waves on the surface of the absorber. The transmission-type electromagnetic-wave absorber includes an electromagnetic-wave absorbing layer 1 containing a magnetic iron oxide 1a that magnetically resonates at a frequency in or above the millimeter-wave band and a binder 1b containing an organic material. The real part of the complex relative permittivity of the electromagnetic-wave absorber is 5.5 or less at 1 GHz.

A radio wave-absorbing laminate film in which both the top surface and the bottom surface have superior transmission attenuation properties and reflection attenuation capabilities in extremely high-frequency wave bands and higher, and which exhibits excellent radio wave absorption properties even when extremely thin; a production method for the film; and an element containing the film. A radio wave-absorbing laminate film having radio wave-absorbing layers, the radio wave-absorbing laminate film including a center layer, two substrate layers, and two radio wave-absorbing layers, the center layer containing at least one metal layer, and the two substrate layers being laminated on both surfaces of the center layer. With regard to each of the two substrate layers, the radio wave-absorbing layer is laminated on the surface opposite to the center layer, and, the two substrate layers are the same or different, the two radio wave-absorbing layers are the same or different, and at least one of the radio wave-absorbing layers contains a magnetic body.

A polycrystalline ferrite composition comprises a formula of M.sub.5Me.sub.2Ti.sub.3Fe.sub.12O.sub.31, wherein M is Ba.sup.2+, Se.sup.+, or a combination thereof; and Me is Mg.sup.2+, Zn.sup.2+, Cu.sup.2+, Co.sup.2+, or a combination thereof; and has an average grain size of 1 micrometer to 100 micrometers. A composite comprises a polymer matrix; and the polycrystalline ferrite composition. Methods of making the polycrystalline ferrite composition and the composite are also disclosed.

Disclosed herein are embodiments of an enhanced resonant frequency hexagonal ferrite material and methods of manufacturing. The hexagonal ferrite material can be Y-phase hexagonal ferrite material, such as those including strontium. In some embodiments, oxides consistent with the stoichiometry of Sr.sub.3Co.sub.2Fe.sub.24O.sub.41, SrFe.sub.12O.sub.19 or CoFe.sub.2O.sub.4 can be used form an enhanced hexagonal ferrite material.

In an aspect, a ferrite composition comprises a BiRuCo-M-type ferrite having the formula Me.sub.1-xBi.sub.xCo.sub.yRu.sub.zFe.sub.12-tO.sub.19, wherein Me is at least one of Sr, Pb, or Ba; x is 0.01 to 0.5; y is 0.1 to 2; z is 0 to 4, and t is 0 to 4; wherein the Co can be at least partially replaced by at least one of Zn, Cu, or Mg by an amount of less than y, and the Ru can be at least partially replaced by at least one of Ti, Sn, or Zr, where the substitution amount is not more than z or is less than z.

In an aspect, a Co.sub.2Z ferrite has the formula: (Ba.sub.1−xSr.sub.x).sub.3Co.sub.2+yM.sub.yFe.sub.24−2y−zO.sub.41. M is at least one of Mo, Ir, or Ru. The variable x can be 0 to 0.8, or 0.1 to 0.8. The variable y can be 0 to 0.8, or 0.01 to 0.8. The variable z can be −2 to 2. The Co.sub.2Z ferrite can have an average grain size of 5 to 100 nanometers, or 30 to 80, or 10 to 40 nanometers as measured using at least one of transmission electron microscopy, field emission scanning electron microscopy, or x-ray diffraction.

Radiofrequency and other electronic devices can be formed from textured hexaferrite materials, such as Z-phase barium cobalt ferrite Ba.sub.3Co.sub.2Fe.sub.24O.sub.41 (Co.sub.2Z) having enhanced resonant frequency. The textured hexaferrite material can be formed by sintering fine grain hexaferrite powder at a lower temperature than conventional firing temperatures to inhibit reduction of iron. The textured hexaferrite material can be used in radiofrequency devices such as circulators or telecommunications systems.

The powder of the magnetoplumbite-type hexagonal ferrite is an aggregate of particles of a compound represented by Formula (1), and, in a particle size distribution based on number measured by a laser diffraction scattering method, in a case where a mode value is defined as a mode diameter, a diameter at a cumulative percentage of 10% is defined as D10 and a diameter at a cumulative percentage of 90% is defined as D90, the mode diameter is equal to or greater than 5 μm and less than 10 μm and an expression of (D90−D10)/mode diameter≤3.0 is satisfied. In Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0.

AFe.sub.(12-x)Al.sub.xO.sub.19  Formula(1)

A method for producing a powder of a magnetoplumbite-type hexagonal ferrite which is an aggregate of particles of a compound represented by Formula (1), the method including: a step A of adjusting a pH of an aqueous solution containing a Fe salt, an Al salt, and at least one metal element salt selected from the group consisting of a Sr salt, a Ba salt, a Ca salt, and a Pb salt to exceed 8.0, thereby obtaining a reaction product; a step B of drying the reaction product obtained in the step A, thereby obtaining a dried product; and a step C of firing the dried product obtained in Step B, thereby obtaining a fired product, and application. In Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0.

AFe.sub.(12−x)Al.sub.xO.sub.19   Formula (1)

A powder mixture of a magnetoplumbite-type hexagonal ferrite is a mixture of powders of two or more kinds of compounds represented by Formula (1), the two or more kinds of compounds represented by Formula (1) are two or more kinds of compounds having different values of x in Formula (1), and are a powder mixture satisfying a relationship of x.sub.max-x.sub.min23 0.2, in a case where a maximum value of x is defined as x.sub.max and a minimum value of x is defined as x.sub.min, in two or more kinds of compounds having different values of x in Formula (1), and the application. In Formula (1), A represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb, and x satisfies 1.5≤x≤8.0.

AFe.sub.(12-x) Al.sub.xO.sub.19   Formula (1)