British and Swiss scientists have developed a 3D imaging technique that allows them to observe complex behaviours in magnets, including fast-moving waves and “tornadoes” thousands of times thinner than a human hair.
Writing in the journal Nature Nanotechnology, they say the technique, called time-resolved magnetic laminography, could be used to understand and control the behaviour of new types of magnets for next-generation data storage and processing.
The work was a collaboration between researchers from the Universities of Cambridge and Glasgow, ETH Zurich and the Paul Scherrer Institute – and it was complex.
Modelling and visualising magnetic behaviour is relatively straightforward in two dimensions, but in three dimensions the magnetisation can point in any direction and form patterns, which is what makes magnets so powerful.
“Not only is it important to know what patterns and structures this magnetisation forms, but it’s essential to understand how it reacts to external stimuli,” says Cambridge’s Claire Donnelly, the paper’s first author.
“These responses are interesting from a fundamental point of view, but they are crucial when it comes to magnetic devices used in technology and applications.”
The new technique uses powerful synchrotron X-rays to probe the magnetic state from different directions at the nanoscale, and how it changes in response to a quickly alternating magnetic field.
The resulting 7D dataset (three dimensions for the position, three for the direction and one for the time) is then obtained using a specially developed reconstruction algorithm, providing a map of the magnetisation dynamics with 70 picosecond temporal resolution, and 50 nanometre spatial resolution.
What the researchers saw with their technique was, they say, like a nanoscale storm: patterns of waves and tornadoes moving side to side as the magnetic field changed. Such movement had previously only been observed in 2D.
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