I need to shield my device from magnetic interference, including earth magnetic field (if you move device around, it might be enough to cause slight currents i guess) and magnetic field caused by power nets, wires with large currents e.t.c .
I know this could be achieved by making case out of mu-metal, but it seems that I can't find it anywhere (especially in small quantities).
So, are the other, easier ways to shield magnetic field? Will multiple sheets of steel work for example?
Answer
Multiple sheets of steel work nicely to attenuate magnetic fields with higher frequencies but they are not great if you want to shield against small and constant fields.
To shield the earth's magnetic field the best material has a high permeability with almost zero hysteresis. There are some metallic glasses, such as Ultraperm, Vitrovac or Metglas that I have tested. Mu-metal is still somewhat exotic, as it needs to be shaped into it's final form and then heat treated and protected against shocks afterwards. It can be magnetized easily and then needs to be demagnetized again (if you need very low DC fields).
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