PhD Project

Domain structure and microwave characteristics of particulate magnetic composites

Magnetic composite and particulate systems have a paramount importance in modern technology, ranging in applications from magnetic recording media to RF communication. In order to broaden the impact and value of these microwave devices, it is essential that research is undertaken to explore how the permeability of these materials can be increased, and to increase the operational frequency and bandwidth over which they have useful magnetic properties. As part of this work, we will also seek to understand and control the permittivity and loss of these materials, for example, for the design of low reflectivity surfaces and impedance matched materials for antenna design.

The aim of this project is to explore experimentally the static and dynamic electromagnetic properties of particulate magnetic composites. We will look at the magnetic properties of single particles, including their domain structure, as a function of their size, shape and crystalline structure: as part of this we will consider what contribution to the electromagnetic properties that dynamic processes such as domain wall oscillations and FMR provide. Having understood this, we will examine their collective response as part of a bulk composite in order to engineer materials designed with bespoke permittivity and permeability parameters. The experiments will be carried out using state-of-the-art synchrotron and neutron facilities, and static magnetometry and microwave techniques. The former, such as XPEEM, will be used to image directly the magnetic structure of a single particle and its dynamic response to the RF excitation, whereas VNA measurements, using strip-line permeameters, will provide broad-band measurement of the electromagnetic parameters of manufactured composites. We will also employ other lab-based tools to understand the main magnetic characteristics (i.e. hysteresis, anisotropy, saturation magnetisation, bulk moment) of the composite.