Decomposition of susceptibility spectra in a torsion-stressed Fe-based amorphous wire

The complex susceptibility spectra are measured as functions of the alternating-current field amplitude and the torsion angle in an Fe77.5Si7.5B15 amorphous wire. The susceptibility spectra show dispersion with a relaxation frequency of 40 kHz due to irreversible motion of the inner core domain walls when the driving field is larger than the threshold field of 10 mOe. The spectra for a small driving field can be decomposed into two relaxation dispersions by using the nonlinear curve fitting, one originating from reversible wall motion of the inner core domains and with a relaxation frequency of 0.36 MHz, and the other originating from reversible magnetization rotation in the outer shell domains and with relaxation frequency of 1.82 MHz. The static susceptibilities resulting from the reversible and the irreversible magnetization processes show an asymmetric change with positive and negative torsion angles. (C) 2000 American Institute of Physics. [S0003-6951(00)01923-9].