Breakthrough in Accessing the Tiny Magnet within the Core of a Single Atom

The two elements that were investigated in this work, iron and titanium, are atoms that can have a different number of neutrons in the atom’s core, these are the so-called isotopes. Only certain isotopes of each element have a core with a nuclear spin. It is normally exceedingly hard to measure nuclear spins of individual atoms. Traditionally large numbers of nuclear spins are required, making this advancement so noteworthy.

In order to detect the presence of a nuclear spin within the core of a single atom, the team made use of the hyperfine interaction. This phenomenon describes the coupling between a single atom’s nuclear spin and its electron counterpart, that is generally much easier to access. Dr. Philip Willke of the Center for Quantum Nanoscience (QNS), first author of the study, says: “We found that the hyperfine interaction of an atom changed when we moved it to a different position on the surface or if we moved other atoms next to it. In both cases, the electronic structure of the atom changes and the nuclear spin allows us to detect that.”

A step closer to single-atom data storage

Physicists of QNS and EPFL used Scanning Tunneling Microscopy to successfully test the stability of a magnet made up of a single atom. Despite the rise of solid-state drives, magnetic storage devices such as conventional hard drives and magnetic tapes are still very common. But as our data-storage needs are increasing at a rate of almost 15 million gigabytes per day, scientists are turning to alternative storage devices. One of these are single-atom magnets: storage devices consisting of individual atoms stuck (“adsorbed”) on a surface, each atom able to store a single bit of data that can be written and read using quantum mechanics. And because atoms are tiny enough to be packed together densely, single-atom storage devices promise enormous data capacities. But although they are no longer science fiction, single-atom magnets are still in basic research, with many fundamental obstacles to be overcome before they can be implemented into commercial devices. EPFL has been at the forefront of the field, overcoming the issue of magnetic remanence, and showing that single-atom magnets can be used to read and write data. Fabio Donati of the IBS Center for Quantum Nano Science, coauthor of the publication, says that “the intriguing behavior of single-atom magnets is interesting both for fundamental science and for future applications. Exploring the limiting factors of their magnetic stability is crucial for engineering future nanoscale devices that can use single atoms as building blocks.”

A Quantum Sensor Made from Individual Iron Atoms

QNS researchers, in collaboration with a team of IBM researchers in the USA have succeeded in using individual iron atoms as quantum sensors. Using this sensor, they were able to measure the small magnetic field created by neighboring magnetic atoms, an effect that was previously not measurable in scanning tunneling microscopy.

This work is the first application of a recent breakthrough invention of the same team, which demonstrated electron spin resonance – a quantum mechanical measurement of single spins – in the STM. “We believe that this quantum sensor can be used to measure the spins in complex molecules with atomic-scale spatial resolution, sort of like a nano-GPS”, suggests Taeyoung Choi, first author of the recent study.