Alperm
Alperm (also alfenol or alfer) - a class of alloys comprising 83-90% of iron and 10-17% of aluminium. The most widely used composition is with 16% Al.[1] The alloy was discovered by Japanese researchers H. Masumoto and Hideo Saito in 1939.
An alloy with 13% Al is also sometimes referred to as alfer. It exhibits large magnetostriction and it is used in magnetoelastic sensors.
Alperm is magnetically soft and exhibits high magnetic permeability, up to 50 000 after annealing. The material can be produced in 0.5 mm thick sheets as well as 50-60 μm thick amorphous ribbons[2].
The addition of Al increases electrical resistivity of alloy up to 140 μΩm, which is almost four times the value in commonly used 3% SiFe electrical steel. For this reason alperm can be used in higher frequency range. However, because of the Al content the material is more susceptible to oxidation.