Spatial extent of the flux due to local irreversible changes of the magnetic polarization in ferromagnetic strips and rods

Abstract

Two experimentally determined functions for 3% silicon-iron strips with Goss texture, part of which have been plastically deformed, are reported. The experiments were done using two short induction coils with variable distance a. The two functions are (i) the normalized cross spectrum K( f, a) of the Barkhausen noise and (ii) the irreverible transfer of locally impressed flux changes along the sample. The normalized cross spectrum was found to be independent of the frequency f at low frequencies, but decaying with the distance a. The transferred flux changes were found to decay exponentially with a characteristic length, which could be changed by plastic deformation or by varying the static homogeneous field. In all these cases, and in the case of an iron rod the characteristic length could be calculated from magnetostatic theory for the large differential permeabilities involved. The low frequency limiting curve of the normalized cross spectrum can be computed quantitatively from the irreversible flux transfer function. The results show that despite the different metallurgical and magnetic domain structures in the investigated cases, the transfer of both externally impressed and spontaneously released irreversible flux changes are governed by magnetostatic principles.