Distribution of the internal stresses in DC Joule-heated Fe77.5B15Si7.5 conventional amorphous microwires

Abstract

The magnetic properties of conventional amorphous microwires are determined by the radial, azimuthal and axial internal stresses induced both during the preparation process and during suitable thermal treatments. We propose a theoretical model in order to determine the total internal stresses induced during the ‘complete’ dc Joule-heating thermal treatment (heating–crystallization–cooling). We have started from the internal stresses values obtained in the preparation process and we have found that: (i) maximal values of the axial, azimuthal and radial stresses obtained after the thermal treatment are larger than the corresponding values obtained in the preparation process, the differences being of about 350 MPa, 150 MPa and 200 MPa, respectively; (ii) the dimensions of the cylindrical inner core increase significantly (with ∼15.2%); this fact involves the appearance of a large Barkhausen effect in low axially applied magnetic fields; and (iii) the reduced remanence increases from 0.46 to 0.70.