Soft Magnetic Materials

Soft magnetic materials are widely used in power electronic circuits, motors, generators, and actuators.  Spectrum Magnetics focuses on the development of the following high frequency soft magnetic materials:

1. Soft magnetic nanocomposite materials for power electronics

2. Spinel ferrites for above 1 MHz applications

3. Electromagnetic interference shielding and microwave absorption materials for above 100 MHz

Soft magnetic materials 1

There are two types of widely used soft magnetic materials: Fe, Ni, and Co alloy based metallic materials for low frequency (<2 kHz) applications, and oxide based ceramic materials (10kHz-1MHz). With an increasing demand for power electronics with a reduced size, weight, and cost, it is necessary to increase the operational frequency above 1MHz. Therefore, Spectrum Magnetics LLC is focused on developing soft magnetic materials with a high operating frequency, permeability, and power capability.

Soft Magnetic Nanocomposites

Spectrum Magnetics has developed soft magnetic nanocomposites with relative permeabilities of 10-80 in the 1-100 MHz frequency range. These soft magnetic nanocomposites can be used in magnetic components such as inductors or transformers, or in various converters operating in multi-MHz. A series of soft magnetic nanocomposites have been developed for applications in different frequency ranges from 100 kHz to 100 MHz, as shown in figures below. This material is anisotropic.

Soft magnetic materials 2

To meet the demand for power electronics with reduced size, weight, and cost, the operational frequency must be increased above 1 MHz. The volume and weight in a converter are mainly determined by passive components, such as the inductors and transformers. Soft magnetic nanocomposite materials are developed with high flux density (Bs) and high Curie temperature (Tc), and greatly reduced eddy current loss.

Spinel Ferrites

Ferrites are non-conductive ferromagnetic ceramic compounds derived from iron oxides, as well as oxides of other metals. The most common soft ferrites are MnZn (MnxZn1-xFe2O4) and NiZn (NixZn1-xFe2O4) ferrites. NiZn ferrites exhibit higher resistivity than MnZn ferrites, and are therefore more suitable for frequencies above 1 MHz. MnZn have a comparably high permeability and saturation induction.

Soft magnetic materials 3

However, commercially available soft magnetic ferrites are not optimized for high frequency applications, especially in multi-MHz frequency ranges. Modified MnZn and NiZn ferrites for multi-MHz high power applications have recently been developed through nanotechnology. These ferrites have high permeability and exhibit low core loss between 1-5 MHz. The ferrites are isotropic, and can be made with in a variety of shapes and sizes.

Electromagnetic Interference Shielding

Electromagnetic interference is radiation emitted from an external source. Electromagnetic interference can adversely affect electrical circuits, cell phones, televisions, satellite communications, GPS, electrical grids, etc. With these electronics so prevalent in today’s world, research into different kinds of shielding to protect against harsh electromagnetic environments is on the rise.

NanoMetaShielding materials can used in various applications such as laptops, GPS, wireless communications, and microwave/radar absorbent materials.

Conventional electromagnetic interference shielding is usually made of highly conductive materials. The shielding’s performance is characterized by the shielding effectiveness, which is affected by reflection, absorption, and other properties. In general, there are two practical solutions for EMI shielding. The first is to protect certain components from external EMI by reflection and/or absorption. The second is to reduce reflection on metal surfaces and dissipate the electromagnetic energy in the form of heat. Spectrum Magnetics LLC focuses on the second type of shielding, also known as microwave absorbent material or radar absorbent materials.

Radar absorbent materials can significantly reduce the radar cross-section of an object at specific frequencies. One of most commonly known radar absorbent materials is iron ball paint, paint that contains tiny spheres coated with carbonyl iron or ferrite. Carbon black or fibers are another important example.

In general, radar absorbent materials can be categorized into four basic types of materials:

1. Dielectric absorbent

2. Magnetic absorbent

3. Resonant absorbent

4. Others

Complex dielectric permittivity (ε = ε’ – iε”) and permeability (μ = μ’ – iμ”) are two important parameters describing the properties of these materials. The imaginary parts of permittivity and permeability are associated with the energy losses. Therefore, good radar absorbent materials usually require a large dielectric loss tangent (ε”/ε’) and magnetic loss tangent (μ”/μ’). Additionally, radar absorbent materials are also made of materials with matched impedance or gradually matched impedance similar to that of air in order to reduce reflection.

Spectrum Magnetics LLC has developed radar absorbent materials based on nanocomposites for various frequency bands from 10 MHz to 10 GHz or higher. The impedance of our radar absorbent materials can be tailored to match that of air.

Product # μ’ @ 10MHz ε’ @ 10MHz  μ”/μ’ @ 10MHz   μ”/μ’ @ 100MHz   μ”/μ’ @ 500MHz   μ”/μ’ @ 1GHz  Datasheet
SMMDF300 230 12 0.3 1.4 5.6 35 SMMDF300
SMMDF301 16 12 <0.001 0.005 1.2 3.2 SMMDF301
SMMDF302 42 13 0.004 0.7 2.1 4.3 SMMDF302