Influence of dislocations on magnetization processes in soft magnetic materials

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 Hc, the initial susceptibility χi, and the dislocation density N showed that Hcvaries as and χiand . The temperature dependence of Hcand χiof 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 Hcof 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 Hcoccurs at lower temperature. The χi-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 χiachieves 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 Hcand χiremain constant up to about 200°C. Above this temperature the Hcincreases to a maximum and then drops gradually with rising temperature, while χidrops to a minimum and then steadily increases with rising temperature. During the isothermal recovery at lower temperatures the Hcexhibits an initial increase followed by gradual drop to lower values. The χidrops initially to a minimum and then increases with annealing time.