The creation of electricity and control of antiferromagnetic vortices is demonstrated in a new study
(Nanowerk News) A new study has shown for the first time how the generation of electricity and the control of magnetic vortices in antiferromagnets can be achieved, a discovery that will increase the data storage capacity and speed of the next generation of devices.
Researchers from the University of Nottingham’s School of Physics and Astronomy have used magnetic imaging techniques to map the structure of newly formed magnetic vortices and demonstrate the alternating motion caused by alternating electrical pulses.
Their findings have been published in Natural Nanotechnology (“The antiferromagnetic half-skyrmion is electrically generated and controlled at room temperature”).
Oliver Amin, Research Fellow at the University of Nottingham and lead author of the study explained: “This is an exciting moment for us, these magnetic vortices have been proposed as carriers of information in the next generation of memory devices, but evidence of their presence in antiferromagnets has so far been scarce. Now, we not only create them, but also move them in a controllable way. This is another success for our material, CuMnAs, which has been at the center of several breakthroughs in antiferromagnetic spintronics over the past few years.”
CuMnAs has a specific crystal structure, growing in an almost complete vacuum, atomic layer by atomic layer. It has been shown to behave like a switch when pulsed with an electric current, and a research group in Nottingham, led by Dr Peter Wadley, along with international collaborators, have ‘zoomed in’ on controlled magnetic textures; first with the demonstration of a moving domain wall, and now with the generation and control of magnetic vortices.
Key to the research was a magnetic imaging technique called photoemission electron microscopy, which was carried out at the British synchrotron facility, Diamond Light Source. The synchrotron generates a beam of collimated polarized x-rays, which are beamed into the sample to investigate the magnetic state. This enables the spatial resolution of micromagnetic textures as small as 20 nanometers.
Magnetic materials have been important technologies for centuries, from compasses to modern hard disks. Yet nearly all of these materials belong to one type of magnetic order: ferromagnetism. These are the types of magnets we are all familiar with from fridge magnets to washing machine motors and computer hard drives. They produce an external magnetic field that we can “feel” because all the magnetic moments of the tiny atoms that compose them tend to align in the same direction. It is this field that causes fridge magnets to stick and we sometimes see them mapped with iron filings.
Because they lack an external magnetic field, antiferromagnets are difficult to detect and, until recently, difficult to control. For this reason they find almost no application. Antiferromagnets do not generate an external magnetic field because all the tiny atomic moments of their neighboring constituents point in opposite directions to one another. In doing so they cancel each other out and no external magnetic field is generated: they won’t stick to the fridge or deflect a compass needle.
But antiferromagnets are magnetically stronger and their tiny atomic moments move about 1000 times faster than ferromagnets. This could create computer memory that operates much faster than current memory technology.
Dr Peter Wadley from the University of Nottingham added: “Antiferromagnets have the potential to outperform other forms of memory which will lead to a redesign of computing architecture, huge speed increases and energy savings. The additional computing power can have a big social impact. This finding is very exciting because it brings us closer to realizing the potential of antiferromagnetic materials to transform the digital landscape.”