Anisotropic behaviour of magneto-electric coupling in multiferroic composites

    Student thesis: Doctoral Thesis


    The anisotropy of the direct magnetoelectric effect in textured nickel ferrite/lead zirconate titanate strain mediated bilayer composites has been studied. The magnetic layers of these samples have been crystallographically textured in planes of the form {100}, {110} and {111}.
    In this study, it is shown that the optimum bias field and the maximum
    magnetoelectric coupling signal can be controlled by changing the alignment of
    the applied magnetic field with respect to the magnetocrystalline anisotropy
    directions. It is also shown that the product of the optimum bias field and the
    maximum magnetoelectric coupling signal are proportional to the theoretical
    saturation magnetostriction.
    The samples have been magnetically characterised using a recommissioned and
    developed biaxial vibrating sample magnetometer, capable of detecting the
    component of a sample’s magnetic moment in 2 perpendicular directions and
    thus determining the net magnetic moment vector of the sample. Coupled with
    sample rotation this allows insight into the magnetic anisotropy of the sample,
    which has been compared with a micromagnetic model.
    A specialist magnetoelectric coupling rig has also been developed to allow
    application of DC and AC magnetic fields to a sample simultaneously.
    As part of the magnetic anisotropy study, a modified torque magnetometry
    method has been developed to enhance the identification of the anisotropy
    directions in magnetically soft samples, as well as a method by which torque
    magnetometry can be approximated using the in-field direction component of
    magnetisation as measured using a standard vibrating sample magnetometer.
    Date of Award1 Nov 2017
    Original languageEnglish
    Awarding Institution
    • University of Central Lancashire
    SponsorsNational Physical Laboratory
    SupervisorTim Mercer (Supervisor), Serban Lepadatu (Supervisor) & Melvin Vopson (Supervisor)


    • multiferroic composites
    • experimental testing
    • vector VSM

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