What Materials Shield Magnets?

Without shielding, magnets in these speakers would interfere with the monitor.
••• Monitor image by Kavita from Fotolia.com

In today’s world we are surrounded by electrical and electronic appliances and gadgets that either produce their own magnetic field, have magnetic components or both. Many of these fields are strong enough to interfere with the operation of our electronic equipment. For instance, without magnetic separation, the magnets in your TV’s speakers would distort the color and image on the TV screen. The materials used to protect components from potentially disruptive magnetic fields are called magnetic shields.

Magnetic Fields

Magnetic fields are produced by magnetic flux, or flow, in a source. The source might be a bar magnet, an electric current through a wire or even the earth itself. Of course, the fields are invisible, but most of us are familiar with the visualization of magnetic lines of force that's created by placing iron filings within a bar magnet's field. Any object in the path of one or more of these magnetic lines of force is within the magnetic field.

When an electronic device is within an electronic field, its performance may be affected by it. This is particularly true of devices that translate magnetic field values into digital data. The fact that you can read this article on your computer screen is evidence that industry has found a way to shield electronic components from magnetic interference.

Magnetic Shield Materials

Magnetic lines of force
••• concentrics image by Adrian Hillman from Fotolia.com

Magnetic shields work by redirecting the force lines away from the shielded object. Because of this, the materials used for magnetic shielding have to be able to sustain a strong magnetic field; that is to say, they have to have a high magnetic permeability. Besides common materials such as iron, nickel and cobalt, there are several proprietary alloys commercially available that are especially designed for use as magnetic shields.

New technologies have provided some new magnetic shielding materials. For instance, nanotechnology has contributed magnetic shield materials that can be applied directly to the component like a coat of paint. While not always practical, superconductors, materials that lose all their electrical resistance at very low temperatures, are excellent magnetic shields.

Other Uses

In some applications, magnetic shield materials can also shield against radio frequency interference. This is interference caused by high-frequency electromagnetic radiation above 100 kilohertz.

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