Nanostructured Fe40Ni38Mo4B18 prepared by crystallization technique has a m
icrostructure of nanometer-sized fee (Fe, Ni) solid solution crystallites e
mbedded in a nanometer-thick amorphous matrix. The nanostructured Fe40Ni38M
o4B18 obtained at 740 K has the optimal soft magnetic properties. The maxim
al magnetic softening can be understood by considering the combination of t
he zero anisotropy and the lowest saturation magnetostriction.