In an aspect, a Co.sub.2Z-type ferrite comprises oxides of at least Me, Co, Mo, Li, and Fe; wherein Me is at least one of Ba or Sr. In another aspect, the Co.sub.2Z-type ferrite comprises a Z-type hexaferrite an amount of lithium molybdate. In another aspect, the Co.sub.2Z-type ferrite has a formula Li.sub.2MoO.sub.4.Ba.sub.xSr.sub.3-xCo.sub.2+y−zMe′.sub.yMe″.sub.zFe.sub.24-2y-mO.sub.41, wherein Me′ is at least one of Ti, Mo, Ru, Ir, Zr, or Sn; Me″ is at least one of Zn, Mn, or Mg; x is 0 to 3; y is 0 to 1.8; z is 0 to 1.8; and m is −4 to 4. In yet another aspect, a method of making a Co.sub.2Z-type ferrite comprises milling an initial Co.sub.2Z-type ferrite and Li.sub.2MoO.sub.4 to form a mixed ferrite; and calcining the mixed ferrite to form the Co.sub.2Z-type ferrite.

A hexagonal ferrite magnetic powder is significantly more useful for achieving simultaneously both the enhancement of the recording density and the enhancement of the SNR of a magnetic recording medium. The hexagonal ferrite magnetic powder contains Bi at a Bi/Fe molar ratio in a range of 0.035 or less, has a saturation magnetization σs of 42.0 Am.sup.2/kg or more and a Dx volume calculated based on the crystallite diameters of 1,800 nm.sup.3 or less. A method for producing hexagonal ferrite magnetic powder includes a step of performing a treatment of immersing hexagonal ferrite magnetic powder containing Bi in a solution having dissolved therein a compound X that forms a complex with Bi, so as to elute a part of Bi existing in the hexagonal ferrite magnetic powder into the solution.

In an aspect, a ferrite composition comprises a Ru—Co.sub.2Z ferrite having the formula: (Ba.sub.3-xM.sub.x)Co.sub.2(M′Ru).sub.yFe.sub.24-2y-zO.sub.41, wherein M is at least one of Sr, Pb, or Ca; M′ is at least one of Co, Zn, Mg, or Cu; x is 1 to 3; y is greater than 0 to 2; and z is −4 to 4. In another aspect, an article comprises the ferrite composition. In yet another aspect, method of making the ferrite composition comprises mixing ferrite precursor compounds comprising Fe, Ba, Co, and Ru; and sintering the ferrite precursor compounds in an oxygen atmosphere to form the Ru—Co.sub.2Z ferrite.

A soft magnetic composition that includes an oxide containing a W-type hexagonal ferrite having a compositional formula of ACaMe.sub.2Fe.sub.16O.sub.27 as a main phase, wherein A is one or more selected from Ba, Sr, Na, K, La, and Bi at 4.7 mol % to 5.8 mol %; Me is one or more selected from Co, Cu, Mg, Mn, Ni, and Zn at 9.4 mol % to 18.1 mol %, the Ca is 0.2 mol % to 5.0 mol %, the Fe is 67.4 mol % to 84.5 mol %, and the soft magnetic composition has a coercivity Hcj of 100 kA/m or less.

There is provided a radio wave absorber containing a magnetic powder, and an aliphatic polyamide, in which an intensity ratio (α/γ) of a diffraction intensity α of an α crystal of the aliphatic polyamide to a diffraction intensity γ of a γ crystal of the aliphatic polyamide, which are determined by subjecting the radio wave absorber to measurement with an X-ray diffraction method, is 2.60 or less. There is also provided a radio wave absorbing article including this radio wave absorber.

In an aspect, a multiphase ferrite comprises a Co.sub.2W phase that is optionally doped with Ru; a CFO phase having the formula Me.sub.r“Co.sub.1−rFe.sub.2+zO.sub.4, wherein Me” is at least one of Ni, Zn, or Mg, r is 0 to 0.5, and z is −0.5 to 6 0.5; and a CoRu-BaM phase having the formula BaCo.sub.x+yRu.sub.yFe.sub.12−(2/3)x−2yO.sub.19, wherein x is 0 to 2, y is 0.01 to 2; and the Ba can be partially replaced by at least one of Sr or Ca. In another aspect, a composite can comprise a polymer and the multiphase ferrite. In yet another aspect, a method of making a multiphase ferrite can comprise mixing and grinding a CoRu-BaM phase ferrite and a CFO phase ferrite to form a mixture; and sintering the mixture in an oxygen atmosphere to form the multiphase ferrite.

Some variations provide a magnetically anisotropic structure comprising a hexaferrite film disposed on a substrate, wherein the hexaferrite film contains a plurality of discrete and aligned magnetic hexaferrite particles, wherein the hexaferrite film is characterized by an average film thickness from about 1 micron to about 500 microns, and wherein the hexaferrite film contains less than 2 wt % organic matter. The hexaferrite film does not require a binder. Discrete particles are not sintered or annealed together because the maximum processing temperature to fabricate the structure is 500° C. or less, such as 250° C. or less. The magnetic hexaferrite particles may contain barium hexaferrite (BaFe.sub.12O.sub.19) and/or strontium hexaferrite (SrFe.sub.12O.sub.19). The hexaferrite film may be characterized by a remanence-to-saturation magnetization ratio of at least 0.7. Methods of making and using the magnetically anisotropic structure are also described.

There is provided a radio wave absorber including a powder of a hexagonal ferrite; and a binder, in which the radio wave absorber has a squareness ratio in a range of 0.40 to 0.60.

There is provided a radio wave absorber including a magnetic powder and a binder, in which a volume filling rate of the magnetic powder in the radio wave absorber is 35% by volume or less, a transmission attenuation amount is 8.0 dB or more, and a reflection attenuation amount is 8.0 dB or more.

There is provided a radio wave absorber including a magnetic powder and a binder, in which a volume filling rate of the magnetic powder in the radio wave absorber is 35% by volume or less, and a volume filling rate of a carbon component in the radio wave absorber is 0% by volume or more and 2.0% by volume or less.