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Mu-metal is a soft magnetic alloy with exceptionally high magnetic permeability. The high permeability of mu-metal provides a low reluctance path for magnetic flux , leading to its use in magnetic shields against static or slowly varying magnetic fields.
Permendur rods. Permendur is a cobalt-iron soft ferromagnetic alloy with equal parts of cobalt and iron which is notable for its high magnetic saturation level. [1] [2] Its saturation flux density of around 2.4 tesla is the highest of any commercially available metal.
Paramagnetism, ferromagnetism, and spin waves. Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet.
To describe a soft ferromagnetic material for technical use, the following parameters are specified: (Relative) permeability Ratio of induction B in the material caused by some field H to an induction in a vacuum in the same field; it is a dimensionless value, as it is relative to a vacuum permeability;
Permeation can occur through most materials including metals, ceramics and polymers. However, the permeability of metals is much lower than that of ceramics and polymers due to their crystal structure and porosity. Permeation is something that must be considered carefully in many polymer applications, due to their high permeability.
Permeability is influenced by the spacing between the grains, which form distributed air gap; the less gap, the higher permeability and the less-soft saturation. Due to large difference of densities, even a small amount of binder, weight-wise, can significantly increase the volume and therefore intergrain spacing.
The concept of permeability is of importance in determining the flow characteristics of hydrocarbons in oil and gas reservoirs, [4] and of groundwater in aquifers. [5]For a rock to be considered as an exploitable hydrocarbon reservoir without stimulation, its permeability must be greater than approximately 100 md (depending on the nature of the hydrocarbon – gas reservoirs with lower ...
Air and vacuum have high reluctance, while easily magnetized materials such as soft iron have low reluctance. The concentration of flux in low-reluctance materials forms strong temporary poles and causes mechanical forces that tend to move the materials towards regions of higher flux so it is always an attractive force (pull).