MIT physicists have recently discovered an excellent example of a fractal arrangement in quantum material, and they published their findings in Nature Communications. This is a world premiere since, until this discovery, such structures have been seen only at much larger scales in the natural world.
The patterns were spotted, surprisingly, in the distribution of magnetic units called ‘domains,’ which develop in a compound called neodymium nickel oxide (NdNiO3). This is a rare metal, an excellent electric conductor, and more.
NdNiO3 has stunning properties
It conducts electricity very easily, and it can become an insulator if you drop it into liquid nitrogen, so it falls below a critical temperature of around minus 123 degrees Celsius (minus 189 Fahrenheit).
Atoms from neodymium nickel oxide gather together as tiny bundles of magnetically oriented particles called domains. The domains can be in a variety of sizes and arrangements, depending on certain quantum interactions.
“We wanted to see how these domains pop up and grow once the magnetic phase is reached upon cooling down the material,” says Comin.
While the scatter with X-rays through the material showed how it distributed its electrons at different temperatures, the scientists needed to invest more knowledge and focus on mapping the size and distribution of its domains.
“So we adopted a special solution that allows squeezing this beam down to a very small footprint, so that we could map, point by point, the arrangement of magnetic domains in this material,” says Comin.
Scientists managed to use a small X-ray beam to detect the scale of magnetic domains across a thin pellicle of NdNiO3.
“The domain pattern was hard to decipher at first, but after analysing the statistics of domain distribution, we realised it had a fractal behaviour,” says Comin.
“It was completely unexpected – it was serendipity.”
A weird phenomenon that occurs is that the neodymium nickel oxide makes the same fractal pattern of domains to reappear when the temperature drops.
“Similar to magnetic disks in spinning hard drives, one can envision storing bits of information in these magnetic domains,” says Comin.
The discovery is huge, because it could lead to new ways of storing and protecting digital information. The key is a better understanding of the domains and their patterns.