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.
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.
Original language | English |
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Awarding Institution |
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Supervisors/Advisors |
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Thesis sponsors |
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Award date | 1 Nov 2017 |
Research Outputs
Development of a method to identify in-plane anisotropy axes in soft magnetic materials using a standard vibrating sample magnetometer
Research output: Contribution to journal › Article › peer-review
ID: 10769610