The multiplication of magnetic domain walls under the effect of induced
currents developed during high frequency magnetization loops is experimentally
investigated in ultra-soft nanocristalline alloys in order to determine the effective
anisotropy and to check the predictions of the Random Anisotropy Model used to explain
their extreme softness. For the first time, direct observation of multiplication is achieved
and resulting effective anisotropy determinations underline the importance of induced
anisotropy upon effective anisotropy.