An alloy is provided which consists of Fe100-a-b-c-d-x-y-zCuaNbbMcTdSixByZz and up to 1 at % impurities, M being one or more of the elements Mo, Ta and Zr, T being one or more of the elements V, Mn, Cr, Co and Ni, Z being one or more of the elements C, P and Ge, 0 at %≦a<1.5 at %, 0 at %≦b<2 at %, 0 at %≦(b+c)<2 at %, 0 at %≦d<5 at %, 10 at %<x<18 at %, 5 at %<y<11 at % and 0 at %≦z<2 at %. The alloy is configured in tape form and has a nanocrystalline structure in which at least 50 vol % of the grains have an average size of less than 100 nm, a hysteresis loop with a central linear region, a remanence ratio Jr/Js of <0.1 and a coercive field strength Hc to anisotropic field strength Ha ratio of <10%.