Influence of dislocations on magnetization processes in soft magnetic materials

Abstract

Dislocations were introduced into specimens of Fe-3.25% Si alloys by plastic deformation and their density and distribution were controlled by annealing at various temperatures. Measurement of the coercive field H c , the initial susceptibility χ i , and the dislocation density N showed that H c varies as \sqrt{N} and χ i and 1/\sqrt{N} . The temperature dependence of H c and χ i of deformed and undeformed specimens was investigated. The coercive field of undeformed specimens stays constant between -196° and 200°C and drop steadily at higher temperatures. The H c of deformed specimens increases to a maximum with rising temperature and then drops steeply near the Curie temperature. With an increase in the degree of deformation the maximum in H c occurs at lower temperature. The χ i -T behavior of the undeformed specimen measured between -196°C, and the Curie temperature exhibits a minimum around room temperature (RT) and a second minimum around 450°C. At the first maximum at 350°C the χ i achieves a magnitude of almost three times its RT value. With increasing deformation the first maximum is gradually flattened. During the isochronal annealing of the deformed specimens between 100°C and 800°C the H c and χ i remain constant up to about 200°C. Above this temperature the H c increases to a maximum and then drops gradually with rising temperature, while χ i drops to a minimum and then steadily increases with rising temperature. During the isothermal recovery at lower temperatures the H c exhibits an initial increase followed by gradual drop to lower values. The χ i drops initially to a minimum and then increases with annealing time.