 This gives it low hysteresis losses when used in AC magnetic circuits.Other high-permeability nickel–iron alloys such as permalloy have similar magnetic properties; mu-metal's advantage is that it is more ductile, malleable and workable, allowing it to be easily formed into the thin sheets needed for magnetic shields.Mu-metal objects require heat treatment after they are in final form—annealing in a magnetic field in hydrogen atmosphere, which increases the magnetic permeability about 40 times.