Microwave applications of soft ferrites

A shielded medical device implanted in a biological organism. The device has a magnetic shield, and the magnetic shield contains a layer of nanomagnetic material; such layer has a morphological density of at least 98 percent; and it is bonded to the medical device by means of an interlayer with a thickness of less than about 10 microns. The nanomagnetic material in such layer has a saturation magnetization of from about 1 to about 36,000 Gauss, a coercive force of from about 0.01 to about 5,000 Oersteds, a relative magnetic permeability of from about 1 to about 500,000, and an average particle size of less than about 100 nanometers.

Magnetically shielded assembly

The present paper reports the complex permittivity, permeability, and microwave absorption properties of core shell type poly (3,4-ethylenedioxy thiophene) (PEDOT) nanocomposite with barium ferrite, synthesized by in situ emulsion polymerization, in the 12.4−18 GHz frequency range. High-resolution transmission electron microscopy (HRTEM) studies reveal the formation of core−shell type morphology with ferrite particles (60−80 nm) as the center while the polymer (PEDOT) formulates the outer shell of the composite. The presence of barium ferrite nanoparticles in the polymer matrix includes the magnetic losses, which mainly arise from the magnetic hysteresis, domain−wall displacement, and eddy current loss. The higher dielectric (e′′ = 23.5) and magnetic loss (μ′′ = 0.22) contributes to the microwave absorption value of 22.5 dB (>99% attenuation) and are found to increase with the amount of ferrite constituents. The polymer was further characterized through Fourier transform infrared spectroscopy (FTIR), ener...

Microwave absorption behavior of core-shell structured poly (3,4-ethylenedioxy thiophene)-barium ferrite nanocomposites.

The need for protecting human or devices from harm and for keeping something from being detected by other instruments is spawning a world of attention in the development of novel electromagnetic (EM) wave absorption materials An ideal EM wave absorber is necessary to have light weight, thin thickness, high EM wave absorption, broad width, tunable absorption frequency, and multi-functionality This article introduces the EM wave absorption mechanism and reviews the development of polymer-based nanocomposites for EM wave absorption, in which polymers act as absorbing components or/and matrixes And we also summarize the approaches to design the ideal absorber, including introduction of nanostructure, and simultaneous action of both dielectric and magnetic materials with special structure by directly mixing, core–shell or multilayer structure

Polymeric nanocomposites for electromagnetic wave absorption

Ferromagnetic microwires enabled multifunctional composite materials

A magnetic sheet made of Fe–Si–Al flakes was found to have excellent permeability and electromagnetic-interferences characteristics in a quasimicrowave band. The flakes prepared by attrition were embedded in a polymer with their planes lying parallel to the sheet plane. This sheet exhibits a peculiar dual dispersion in permeability. The Curie temperature of the flakes increases with increasing specific surface area of the flakes. This suggests the composition of the flakes changes to excess Fe by oxidation of Si and Al. This deviation from the Sendust composition brings an increase of a magnetoelastic effect and the dual frequency dispersion seems to be associated with stress caused by attrition. On the basis of these results, flakes with more desirable permeability characteristics were produced from raw powder with less Fe content. Consequently, we could fabricate a magnetic composite that possesses superior noise suppressing effect in a quasi-microwave band.

Permeability and electromagnetic-interference characteristics of Fe–Si–Al alloy flakes–polymer composite

An electromagnetic interference suppressing body is provided for suppressing electromagnetic interference by undesirable electromagnetic waves. The body can have a conductive support element and a non-conductive soft magnetic layer provided on at least one surface. The electromagnetic interference suppressing body may be used in circuit board electronic equipment and in a hybrid integrated circuit element having an active element and a passive element mounted on a circuit board.

Electronic device having the electromagnetic interference suppressing body

A composite magnetic material is provided for use as an electromagnetic interference suppressor member for effectively suppressing an electromagnetic interference within a high frequency apparatus including a mobile communication terminal. The composite magnetic material consists essentially of a soft magnetic powder and an organic binder and is electrically non-conductive and has at least two magnetic resonances caused by at lest two anisotropic magnetic fields (Hk). In the composite magnetic material, the anisotropic magnetic fields (Hk) are different in strength from each other.

Composite magnetic material and product for eliminating electromagnetic interference

A composite magnetic material is provided for use as an electromagnetic interference suppressing body for effectively suppressing an electromagnetic interference within a high frequency apparatus including a mobile communication terminal. The composite magnetic material consists essentially of a soft magnetic powder and an organic binder and is electrically non-conductive and has at least two magnetic resonances caused by at least two anisotropic magnetic fields (Hk). In the composite magnetic material, the anisotropic magnetic fields (Hk) are different in strength from each other.

Composite magnetic material and electromagnetic interference suppressor member using the same

A tube for externally covering or bundling electric cables is provided for suppressing radiation of undesired electromagnetic waves. The tube is made of a material in which soft magnetic powder is mixed with and dispersed into an organic binding agent. For protecting the cable from the undesired electromagnetic waves from the exterior, it is preferable to provide a conductor layer at an outer side of a composite magnetic layer. For facilitating mounting onto the cable, the tube is provided with a slit in a longitudinal direction. Alternatively, the cable may have a spiral structure. As an organic binding agent, it is preferable to use an elastomer which is excellent in extensible property. Further, it is preferable that the soft magnetic powder is powder being essentially flat.

Mitsuharu Sato

Papers

Permeability and electromagnetic-interference characteristics of Fe–Si–Al alloy flakes–polymer composite

Electronic device having the electromagnetic interference suppressing body

Composite magnetic material and product for eliminating electromagnetic interference

Composite magnetic material and electromagnetic interference suppressor member using the same

Composite magnetic tube and method of producing the same, and electromagnetic interference suppressing tube