Some variations provide a magnetically anisotropic structure comprising a magnetically anisotropic film on a substrate, wherein the magnetically anisotropic film contains a plurality of discrete magnetic hexaferrite particles, wherein the film is characterized by an average film thickness from 1 micron to 5 millimeters, and wherein the magnetically anisotropic film contains from 2 wt % to 75 wt % organic matter. Some variations provide a magnetically anisotropic structure comprising an out-of-plane magnetically anisotropic film on a substrate, wherein the magnetically anisotropic film contains a plurality of discrete magnetic hexaferrite particles, wherein the film is characterized by an average film thickness from 1 micron to 5 millimeters, and wherein the magnetically anisotropic film contains a concentration of hexaferrite particles of at least 40 vol %. The magnetically anisotropic structures are fabricated at low temperatures so that the magnetically anisotropic film may be monolithically integrated into an integrated-circuit fabrication process.

A ferrite magnet includes: a hexagonal ferrite main phase; and a second phase. The second phase is an oxide phase containing: an element A which is at least one selected from the group consisting of Ca, Sr, Ba, Bi, and rare earth elements; a transition metal element T including at least Fe; and an element G which is at least one selected from the group consisting of Si, Al, B, F, K, Na, Li, P, and S. When the total number of atoms of the element A, the transition metal element T, and the element G in the second phase is set to 100 at %, the element A occupies 30 to 80 at %, the element G occupies 15 to 40 at %, and the transition metal element T occupies less than 4 at %.

Herein discussed is a method of sintering a ceramic comprising (a) providing an electromagnetic radiation (EMR) source; (b) (i) providing a layer of intermixed ceramic particles and absorber particles, wherein the absorber particles have a volume fraction in the intermixed particles in the range of no less than 3%; or (ii) providing a first layer comprising ceramic particles and a second layer comprising absorber particles in contact with at least a portion of the first layer, wherein the second layer is farther from the EMR source than the first layer; (c) heating (i) the layer of intermixed particles or (ii) the first layer using EMR; and (d) controlling the EMR such that at least a portion of the ceramic particles are sintered wherein (i) the layer of intermixed particles becomes impermeable or (ii) the first layer becomes impermeable, wherein the absorber particles have greater EMR absorption than the ceramic particles.

The invention provides a ceramic composite oxide of formula (I): (1−x)AaBbOy+xCcDdOz (I) wherein A, B, C and D are each independently selected from the group consisting of Li, Na, Mg, Al, P, K, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Er, Tm, Yb, Lu, Ta, W, Bi and mixtures thereof; x is 0.05 to 0.95; y and z are balanced by the charge of the cations; 0≤a, b, c, d≤1; and wherein said ceramic composite oxide has an average particle size diameter of 10 to 700 nm.

Disclosed herein are embodiments of composite hexagonal ferrite materials formed from a combination of Y phase and Z phase hexagonal ferrite materials. Advantageously, embodiments of the material can have a high resonant frequency as well as a high permeability. In some embodiments, the materials can be useful for magnetodielectric antennas.

Disclosed herein are embodiments of an enhanced resonant frequency hexagonal ferrite material and methods of manufacturing. The hexagonal ferrite material can be Y-phase strontium hexagonal ferrite material. In some embodiments, sodium can be added into the crystal structure of the hexagonal ferrite material in order to achieve high resonance frequencies while maintaining high permeability.

Disclosed herein are embodiments of an enhanced resonant frequency hexagonal ferrite material, such as Y-phase hexagonal ferrite material, and methods of manufacturing. In some embodiments, sodium or potassium can be added into the crystal structure of the hexagonal ferrite material in order to achieve improved resonant frequencies in the range of 500 MHz to 1 GHz useful for radiofrequency applications.

Disclosed herein are embodiments of modified z-type hexagonal ferrite materials having improved properties that are advantageous for radiofrequency applications, in particular high frequency ranges for antennas and other devices. Atomic substitution of strontium, aluminum, potassium, and trivalent ions can be used to replace certain atoms in the ferrite crystal structure to improve loss factor at high frequencies.

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.