New film offers magnetic performance

A team at Sheffield University is attempting to develop a magnetic film that could be used in magnetic micro-electromechanical systems (MagMEMS), a technology exploiting the ‘magnetostrictive’ properties of magnetic materials — their ability to change length in a magnetic field.

This property could allow the film to be used in a range of applications, such as magnetic tags for use as heathcare biosensors, for identifying consumer goods, and lab-on-a-chip technology for analysing substances.

The researchers have already achieved proof of principle for using MagMEMS technology for a hearing implant. Dr Nicola Morley, lecturer in the university’s department of engineering materials, has received funding from the EPSRC to investigate making magnetic film from Iron Gallium (Fe-Ga) — potentially the most magnetostrictive alloy yet.

This alloy has only been tested in bulk and Morley believes that if a film can be made from it, it could be a ground-breaking step in the development of MagMEMS.

‘As a bulk material, Fe-Ga is at least four times as magnetostrictive as some other materials,’ she said. ‘But we do not know yet how it will react as a film.’

The difference with manufacturing a film from Fe-Ga, as opposed to other common ‘smart’ magnetic alloys such as iron cobalt, is that it has an extremely low melting point of only 30º.

The researchers will have to use a specially designed fabrication chamber to evaporate the Fe-Ga. They will then heat and rotate the substrate to study changes in the alloy’s magnetostrictive properties.

‘This is the first chance to really study how these smart magnetic materials change with different fabrication techniques,’ said Morley. ‘We will also discover how useful Fe-GA might be as magnetic film.’