The Influence of Crystal Defects on the Magnetic Behavior of Magnetite

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9304520 Moskowitz A major goal of this proposal is to study the influence of crystal defects on magnetic behavior in magnetite and titanomagnetite. Crystal defects can act as centers for the nucleation of new domain walls and aid changes in magnetization, or they can pin existing domain walls and inhibit changes in magnetization. Aside from some rudimentary details, there is a lack of quantitative knowledge about wall-defect interactions. Specifically, defect structures will be changed and manipulated in a controlled manner by bulk plastic deformation, by single grain micro-indentation, and by thermal annealing experiments. The main purpose of these experiments will be to determine how coercivity and remanence varies with the degree of deformation and with recovery through annealing and to assess critically recent theoretical micromagnetic models for the thermal dependence of coercivity produced by specific types and arrangements of defects. ***