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Mu-metal has several compositions. One such composition is approximately 77% nickel, 16% iron, 5% copper, and 2% chromium or molybdenum. [1] [2]More recently, mu-metal is considered to be ASTM A753 Alloy 4 and is composed of approximately
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.
They also have high magnetic permeability. These so-called ceramic magnets are cheap, and are widely used in household products such as refrigerator magnets . The maximum magnetic field B is about 0.35 tesla and the magnetic field strength H is about 30–160 kiloampere turns per meter (400–2000 oersteds ). [ 33 ]
The most common soft ferrites are: Manganese-zinc ferrite (MnZn, with the formula Mn a Zn (1−a) Fe 2 O 4). MnZn have higher permeability and saturation levels than NiZn. Nickel-zinc ferrite (NiZn, with the formula Ni a Zn (1−a) Fe 2 O 4). NiZn ferrites exhibit higher resistivity than MnZn, and are therefore more suitable for frequencies ...
Magnetically hard materials have high coercivity, whereas magnetically soft materials have low coercivity. The overall strength of a magnet is measured by its magnetic moment or, alternatively, its total magnetic flux. The local strength of magnetism in a material is measured by its magnetization.
Different materials have different saturation levels. For example, high permeability iron alloys used in transformers reach magnetic saturation at 1.6–2.2 teslas (T), [4] whereas ferrites saturate at 0.2–0.5 T. [5] Some amorphous alloys saturate at 1.2–1.3 T. [6] Mu-metal saturates at around 0.8 T. [7] [8]
Below 912 °C (1,674 °F), iron has a body-centered cubic (bcc) crystal structure and is known as α-iron or ferrite. It is thermodynamically stable and a fairly soft metal. α-Fe can be subjected to pressures up to ca. 15 GPa before transforming into a high-pressure form termed ε-Fe discussed below.
Sendust composition is typically 85% iron, 9% silicon and 6% aluminium. The powder is sintered into cores to manufacture inductors. Sendust cores have high magnetic permeability (up to 140 000) [ clarification needed ] , low loss, low coercivity (5 A/m) good temperature stability and saturation flux density up to 1 T [ clarification needed ] .