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.

A radio wave absorber including a radio wave absorbing layer containing a magnetic powder and a binder, in which a metal layer is not provided, a filling rate of the magnetic powder in the radio wave absorbing layer is 35% by volume or less, and in a case where the filling rate of the magnetic powder in the radio wave absorbing layer is denoted by P % by volume and a thickness of the radio wave absorbing layer is denoted by Q mm, the following relationship is satisfied, 0.65≤(P/100)×Q, and the compound.

A magnetic composite includes a polymeric substrate and a magnetic material including a Z-type phase and represented by the following Chemical Formula:

Ba.sub.1.5-xSr.sub.1.5-xCa.sub.2xM.sub.2Fe.sub.24O.sub.41  Chemical Formula

wherein, in the Chemical Formula, M is at least one selected from Co, Ni, Cu, Mg, Mn, Ti, Al, Zn, and Zr, and 0≦x<0.3.

A sintered ferrite magnet comprising (a) a ferrite phase having a hexagonal M-type magnetoplumbite structure comprising Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of Ca.sub.1-x-yR.sub.xA.sub.yFe.sub.2n-zCo.sub.z, wherein the atomic ratios (1-x-y), x, y and z of these elements and the molar ratio n meet the relations of 0.3≦(1-x-y)≦0.65, 0.2≦x≦0.65, 0≦y≦0.2, 0.03≦z≦0.65, and 4≦n≦7, and (b) a grain boundary phase indispensably containing Si, the amount of Si being more than 1% by mass and 1.8% or less by mass (calculated as SiO.sub.2) based on the entire sintered ferrite magnet, and its production method.

An oxide ceramic having a principal component formed of a ferrite compound containing at least Sr, Co, and Fe, and zirconium in an amount of 0.05 to 1.0 wt. % on an oxide equivalent basis, and a ceramic electronic component using the oxide ceramic.

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.

A magnetoplumbite-type hexagonal ferrite powder containing a powder of a magnetoplumbite-type hexagonal ferrite represented by Formula (1) and a powder of a compound represented by Formula (2), in which a magnetic field strength Hα, which corresponds to 90% of a magnetization quantity obtained in a case where an external magnetic field of 50 kOe is applied, satisfies 19 kOe≤Hα≤28 kOe, a radio wave absorber, and a method of controlling resonance frequency of a magnetoplumbite-type hexagonal ferrite powder are provided. 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. In Formula (2), A.sup.a represents at least one metal element selected from the group consisting of Sr, Ba, Ca, and Pb.

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

A.sup.aAl.sub.2O.sub.4  Formula (2)

An electromagnetic, EM, component operational at a defined operating frequency, includes: a body of material having at least one magneto-dielectric material, MDM, with a magnetic material having a relative permeability greater than one and dielectric material having a relative permittivity greater than one, at the defined operating frequency; wherein the magnetic material has one of: a multi-phase crystal structure; or, a non-cubic crystal structure; and, wherein the EM component is at least one of; an EM resonator, and an EM beam shaper.

There is provided a radio wave absorbing composition containing a magnetic powder and a binder. There is also provided a radio wave absorber containing a magnetic powder and a binder. The magnetic powder is a powder of a substitution-type hexagonal ferrite subjected to surface treatment with a surface treatment agent, and the binder is a polyamide.

There is provided a radio wave absorbing composition containing a magnetic powder and a binder. There is also provided a radio wave absorber containing a magnetic powder and a binder. The magnetic powder is a powder of a substitution-type hexagonal ferrite subjected to surface treatment with a surface treatment agent, the surface treatment agent is a silicon-based compound, and the binder is an olefin-based resin.