New magnetic materials for sensor devices
Supervisors: Rachel Edwards and Martin Lees
There is a strong and growing demand for permanent magnets for use in, for example, sensors and
engines, with a push to develop new magnetic materials which will maintain their performance at
higher temperatures (> 400 K). Most of the current permanent magnetic materials contain rareearths, and the growing demand and instability of the supply of rare-earths presents a challenge.
The development of magnetic materials with higher Curie temperatures (Tc) and characterisation of
their properties is key to understanding their behaviour, and producing viable alternatives to enable
the building of new, high temperature sensors.
Through a collaboration with Professor Julie Staunton in the Theory Group, researchers from the
Superconductivity & Magnetism and the Ultrasound groups are developing experiments and the
theoretical basis for understanding the behaviour of new rare-earth - transition-metal permanent
magnets. Polycrystalline and single crystal samples of materials such as SmCo5, GdFe2, and GdCo5
will be produced and then characterised using a range of experimental techniques. These include
magnetometry, transport measurements over a range of temperatures and magnetic fields, and
ultrasonic investigation of the elastic properties of the materials. The results obtained will be used to
understand the behaviour of the materials and identify suitable alternatives to those currently used
for producing permanent magnets.
The materials showing most promise will be formed into bonded permanent magnets and used to
build test sensor devices. The sensor proposed is the electromagnetic acoustic transducer (EMAT),
which is used to perform ultrasonic testing without the need for couplant. These typically contain a
NdFeB permanent magnet, with the maximum inspection temperature limited by Tc and the
availability of water cooling. Measurements using these sensors at elevated temperatures will give
an understanding of the anisotropy of the magnetic materials, their behaviour at higher
temperatures, and show the potential for operation of sensors based on the materials.
The main focus of this project is on material characterisation, and developing an understanding of
their behaviour. Training in sample production will also be provided. There is potential for some
industrial engagement with companies who have requirements for high temperature sensing.
For further information about the project, please contact Dr Rachel Edwards or Dr Martin Lees,
r.s.edwards@warwick.ac.uk, m.r.lees@warwick.ac.uk.