Under certain conditions, a graphene-like material can switch from an insulator to a conductor, something once thought impossible by the laws of physics.
A team from the University of Cambridge has been tinkering around with something similar to the atom-thin ‘wonder material’ known as graphene and has achieved something that could be used in the development of next-generation electronics and memory storage devices.
Publishing their findings in Physical Review Letters, the researchers described how, using iron trithiohypophosphate (FePS3) – commonly called ‘magnetic graphene’ – it is possible for the material to switch from an insulator to a conductor under high pressure.
Unlike the regular graphene, FePS3 was first synthesised in the 1960s. While both share a 2D form, FePS3 is magnetic, whereas graphene isn’t. Despite graphene’s extraordinary strength and conductivity, the fact that it is not magnetic limits its application in areas such as magnetic storage and spintronics, and so researchers have been searching for magnetic materials that could be incorporated with graphene-based devices.
Magnetism in 2D
For this study, the researchers squashed layers of FePS3 together under high pressure of approximately 10 gigapascals. This revealed the material was capable of a ‘Mott transition’, the state at which it can switch between being an insulator and conductor, the latter of which can be tuned by changing the pressure.
These materials are characterised by weak mechanical forces between the planes of their crystal structure. Under pressure, the planes are pressed together, gradually pushing the system from three to two dimensions, and from insulator to metal.
“Magnetism in 2D is almost against the laws of physics due to the destabilising effect of fluctuations, but in this material it seems to be true,” said Dr Sebastian Haines, first author of the paper.
Because the materials are inexpensive, non-toxic and easy to synthesise, they could soon be incorporated into graphene-based devices.
“We are continuing to study these materials in order to build a solid theoretical understanding of their properties,” Haines said. “This understanding will eventually underpin the engineering of devices, but we need good experimental clues in order to give the theory a good starting point.”