New logic

UK researchers have demonstrated that the functions usually associated with transistor-based digital electronics can be emulated in all-metallic nanoscale devices made from ferromagnetic materials.

A team of researchers from DurhamUniversity, Imperial College London and University of Sheffieldhave demonstrated that the functions usually associated with transistor-based digital electronics can be emulated in all-metallic nanoscale devices made from ferromagnetic materials.

The technology is based on the discovery by Professor Cowburn of Imperial’s Department of Physics that it is possible to reproduce the key functions of semiconductor electronics in microchips using only the ‘spin’ of electrons, which is responsible for magnetism, rather than the more conventional ‘charge’ that traditional microchips use.

In the nanomagnetic logic devices the researchers have created, Boolean states are represented by magnetisation in the same fashion as Magnetic Random Access Memory (MRAM). Unlike MRAM, however, magnetic signals can be transported from one part of a device to another by the passage of domain walls through magnetic nanowires and logical operations can be performed on the signals.

These devices could be described as ‘MRAM that can think’ – in other words devices that not only use spin direction to store digital information but which can also manipulate and process it.

The micrograph above shows eleven nanomagnetic logic gates connected in series to form a working digital serial shift register.

The devices that the researchers have fabricated so far – a working NOT-gate and an 11-stage serial shift register/digital frequency divider – require no silicon and require no multilayer processing. That means they can be manufactured at very low cost on flexible substrates, while offering non-volatility, radiation hardness and several hundreds of MHz of bandwidth.

The team is now working with commercial partners to develop the technology and is currently building a more advanced demonstrator chip.