US 12,272,475 B2 · Magnetically anisotropic binder-free films containing discrete hexaferrite nanoplatelets

Abstract

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 (BaFe12O19) and/or strontium hexaferrite (SrFe12O19). 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.

Claims39

Dependent claims

A method of making a magnetically anisotropic structure, said method comprising:

(a) synthesizing or obtaining magnetic hexaferrite particles;
(b) if said magnetic hexaferrite particles are agglomerated, mechanically treating said magnetic hexaferrite particles to form discrete particles;
(c) combining said magnetic hexaferrite particles with a solvent, to generate a dispersion;
(d) depositing said magnetic hexaferrite particles onto a substrate via drying and/or charge-titration assembly, to generate a magnetically anisotropic film of aligned, discrete magnetic hexaferrite particles disposed on said substrate;
(e) optionally embedding said magnetically anisotropic film in a polymer;
and
(f) recovering a magnetically anisotropic structure containing said magnetically anisotropic film, said substrate, and, if present, said polymer,
wherein the maximum processing temperature during said method is 500° C. or less, and
wherein said discrete magnetic hexaferrite particles are aligned with a full width at half maximum angular distribution of the hexaferrite particle c-axis direction of about ±20° or less.

6 more elements

Dependencies are inferred from the claim text.

Magnetically anisotropic binder-free films containing discrete hexaferrite nanoplatelets

Life of this patent

Magnetically anisotropic binder-free films containing discrete hexaferrite nanoplatelets

Life of this patent

Abstract

Claims39