AFMNET: a network on antiferromagnetic materials and ultrafast magnetic processes

Within a ferromagnet (FM), each atom has a magnetic moment that behaves like a bar magnet with a north and south pole, and all atomic moments align in parallel to produce a macroscopic magnetic moment. In 1932, Louis Néel proposed the existence of antiferromagnetic (AFM) materials in which each atomic moment is instead aligned antiparallel to its immediate neighbours. The magnetic fields from individual atoms then cancel out at the atomic scale, causing Néel to remark that AFMs would be useless for all practical purposes. However, recent breakthroughs have shown how electric currents, electric fields, or laser light can modify the orientation of magnetic moments within AFMs, and that the direction of the moments may be read out with polarised light or using electrical contacts. AFMs may conduct and even amplify a current of electronic angular momentum, while magnetic moments within AFMs may be rotated more than 100 times faster than within FMs. In fact, it is possible to change the alignment of magnetic moments within both FMs and AFMs on timescales of about 1 picosecond (1 trillionth of a second), by controlling the transfer of angular momentum within the material following ultrafast laser excitation. Advances in information and communication technology (ICT) have enabled the dawn of the digital age, but at the cost of spiralling energy consumption. Worst case projections are for production and operation of ICT systems to consume 21% of global electricity supply by 2030. Rather than building more data centres, the solution is to develop devices that process and store more data while using less energy. Devices based on magnetic materials are extremely attractive for their non-volatility (information is retained when powered off), while use of AFMs favours greater device density, since the absence of stray magnetic fields avoids cross-talk, and increased speed. For example, magnetic random access memory (MRAM) based on FMs is being developed for computer cache, but increased storage capacity could be realized by instead using an AFM and rotating its magnetic moments through 90° to represent a binary 0 or 1. AFMs could be used to construct ultra-compact magnetic field sensors that enable increased data densities within hard disk drives (HDDs), while ultrafast all-optical switching (AOS) of magnetic order could remove the need for pulsed magnetic fields within a HDD, greatly reducing the complexity of the recording head and the energy required for both its manufacture and operation. AOS could also be exploited in non-volatile all-optical devices for energy efficient telecommunications, or for gating magnetic elements that generate magnetic fields for use in quantum computation. The potential benefits of AFMs extend beyond data storage to brain-like computation, nanoscale sources and detectors of THz frequency radiation, and angular momentum amplifiers to deliver fan-out in spintronic systems. AFM coupled nanostructures are attractive for use in magnetic hyperthermia as a cancer therapy to avoid agglomeration within biological tissue, while AFM minerals may contain information about the earth and solar system in the distant past. The aim of AFMNET is to build an interdisciplinary community to deliver UK leadership in the science of AFMs and ultrafast magnetic processes so that the UK can reap the benefits that they provide.