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The magnetic flux density (B) and applied magnetic field strength (H) for a particular material can be plotted against one another to produce a curve called a B(H) curve. Depending upon the type of material plotted, the curves will look different and information about its magnetic properties may be deduced.


A ferromagnetic material such and iron or MuMetal® , will have a B(H) curve as the graphs below. As the applied magnetic field strength increases, the magnetic flux density increases rapidly up to a limit, or saturation value. The existence of a saturation point in the flux density of a ferromagnetic material can be explained by the crystalline structure of the material itself. Taking MuMetal® as an example, the heat treatment we provide to all of our magnetic shields establishes an increased number of magnetic “domains” within the material which have their own magnetic orientation. These magnetic domains are, in the absence of an external magnetic field, randomly orientated. As an increasing field is applied to the magnetic shield, these “domains” gradually align themselves with it until the point at which all of the domains are aligned to the field. This is called the saturation point and is found to exist at 0.75T for MuMetal® and 1.6T for Supra-50. The domain property of heat treated MuMetal® is what makes it the most suitable material for magnetic shielding.

 


 

 

 

 

 

 

 

 

 

 

 

Data accurate for ring samples 36 x 25 x 0.34 mm having been heat treated at 1150°C for 4 hours and cooled at 250°C per hour 

Headcorn Road  |  Staplehurst  |  Tonbridge  |  Kent  |  TN12 0DS  |  UK

Tel : +44 (0) 1580 891521  Fax : +44 (0) 1580 893345

® MuMetal is a registered trademark of Carpenter Technology Corporation
® MuRoom is a registered trademark of Magnetic Shields Limited
® Cryophy is a registered trademark of Aperam Alloys

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