Barkhausen Effect in Iron, Nickel and Permalloy. I. Measurement of Discontinuous Change in Magnetization

Abstract

These experiments show that the changes in magnetization which take place suddenly in large groups of atoms account quantitatively for the whole change in magnetization which corresponds to the steeper part of the hysteresis loop. Since it is estimated that discontinuities corresponding to groups of ${10}^{10}$ atoms (${10}^{-13\mathrm{}}$ ${\mathrm{cm}}^3$) or less will not appreciably affect the measuring system, it is concluded that the magnetic moments of only a very small number of atoms are reversed in groups smaller than this. The maximum size of the discontinuities for all materials examined, independent of crystal size, is found to be about the same, corresponding to the complete reversals of the elementary magnets contained in a volume of about ${10}^{-6\mathrm{}}$ ${\mathrm{cm}}^3$. The discordance of the results of previous measurements by others is explained as due to the different rates of decay of eddy-currents in the samples used.