BARKHAUSEN EFFECT IN IRRADIATED PURE IRON AND NICKEL

The effect of electron and neutron irradiation on the Barkhausen effect and coercive force of pure iron and nickel were investigated. The investigation was designed to establish whether (l) the Barkhausen effect can provide a sensitive indication of the presence of large radiation-induced defect clusters and whether (2) study of the Barkhausen effect could provide meaningful information about behavior of such defects. (These aims were based on the hypothesis that the Barkhausen effect arises from impedance of domain wall motion by defects having dimensions comparable to the domain wall thickness.) Results indicate that the Barkhausen effect is a more sensitive indicator of radiation damage in magnetic materials than is the coercive force. However, the smallness of the effect after neutron irradiation is puzzling. Based on estimates of the number of high-energy primary recoils produced by neutrons, the observed changes were several orders of magnitude too small. This result may indicate that the concentration of defects generated in the path of high-energy primary recoils is too small to impede domain wall motion appreciably. (Author)