A recent study demonstrated for the first time how electrical creation and regulation of magnetic vortices in an antiferromagnet could be accomplished, a finding that would boost the data storage capacity and speed of next-generation devices.
Image Credit: University of Nottingham
Magnetic imaging techniques were utilized by researchers from the University of Nottingham’s School of Physics and Astronomy to study the structure of newly created magnetic vortices and demonstrate their back-and-forth movement caused by alternating electrical pulses. Their findings were reported in the journal Nature Nanotechnology.
This is an exciting moment for us, these magnetic vortices have been proposed as information carriers in next-generation memory devices, but evidence of their existence in antiferromagnets has so far been scarce. Now, we have not only generated them, but also moved them in a controllable way. It’s another success for our material, CuMnAs, which has been at the center of several breakthroughs in antiferromagnetic spintronics over the last few years.
Oliver Amin, Study Lead Author and Research Fellow, University of Nottingham
CuMnAs have a distinct crystal structure formed atomic layer by atomic layer in a nearly complete vacuum. When pulsed with electrical currents, it behaves like a switch, and the Nottingham research group, headed by Dr. Peter Wadley, has “zoomed in” on the magnetic textures being regulated, first with the illustration of moving domain walls, and now with the formation and regulation of magnetic vortices.
This study relies heavily on a magnetic imaging technique known as photoemission electron microscopy, performed at the UK’s synchrotron facility, Diamond Light Source. A collimated beam of polarised X-Rays is produced by the synchrotron and is shone upon the sample to investigate its magnetic state. This enables spatial resolution of micromagnetic patterns as fine as 20 nm.
Magnetic materials have been technologically important for centuries, from the compass to modern hard discs. Most of these materials, however, have belonged to a single magnetic order: ferromagnetism. This is the type of magnet that most people are familiar with, ranging from fridge magnets to washing machine motors and computer hard discs.
Since all of the tiny atomic magnetic moments that comprise them prefer to align in the same direction, they generate an external magnetic field that one can “feel.” This field is what enables fridge magnets to stick and what is seen mapped out with iron filings.
Antiferromagnets are difficult to detect and, until recently, difficult to manage because they lack an external magnetic field. As a result, they have found almost no applications. Because all of the nearby constituent small atomic moments point in exactly opposite directions, antiferromagnets produce no external magnetic field. They cancel each other out, resulting in no external magnetic field: they do not stick to fridges or deflect a compass needle.
However, antiferromagnets are magnetically stronger, and the movement of their tiny atomic moments occurs 1000 times faster than in a ferromagnet. This could result in computer memory that is far faster than present memory technologies.
Antiferromagnets have the potential to out-compete other forms of memory which would lead to a redesign of computing architecture, huge speed increases, and energy savings. The additional computing power could have a large societal impact. These findings are really exciting as they bring us closer to realizing the potential of antiferromagnet materials to transform the digital landscaped.
Dr. Peter Wadley, Research Lead, University of Nottingham
Journal Reference:
Amin, O. J., et al. (2023). Antiferromagnetic half-skyrmions electrically generated and controlled at room temperature. Nature Nanotechnology. doi.org/10.1038/s41565-023-01386-3.