Mu-metal is a
nickel-
iron alloy (77% nickel, 15% iron, plus
copper and
molybdenum) that is very efficient for screening
magnetic fields. It is used to shield vacuum chambers for experiments with low-energy
electrons.
The name of the material refers to the Greek letter μ, which is the symbol for magnetic permeability. Mu-metal has a high value of μ.
All Wikipedia text
is available under the
terms of the GNU Free Documentation License