Microscopic disorder, finite temperatures and spin waves in domain-wall driven exchange bias

Joo-Von Kim

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated] Exchange bias is an interface effect that results from the exchange interaction between a ferromagnet in contact with an antiferromagnet layer. The existence of bias depends on the magnetic order in the antiferromagnet and the effect is commonly characterized by a hysteresis loop displacement along the field axis and enhancements to the coercivity in the ferromagnet. These features are sensitive to the details of the physical and chemical structure of the ferromagnet/antiferromagnet interface. Although exchange bias was discovered over forty years ago, there still remains a host of unanswered questions and contradictions between experimental observations and theoretical predictions. The problem poses many challenges to test our current understanding of interfacial magnetism and frustrated spin systems.
    A theoretical study of exchange bias in bilayer systems, based on partial domain wall formation near the interface in the antiferromagnet, is presented in this dissertation. A continuum theory developed for mixed interfaces demonstrates a link between microscopic spin order and phenomenological bilinear and biquadratic terms coupling the two magnetic layers. Particular attention is given to the role of impurities, such as interface roughness in the form of geometrical imperfections and magnetic defects within the film layers.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • The University of Western Australia
    DOIs
    Publication statusUnpublished - 2002

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