Scientists have successfully measured the spins of a single atom, executing the world's smallest MRI.

Magnetic resonance imaging measures the density of atomic spins, the electromagnetic properties of electrons and protons, inside the human body. Most MRI scans measure millions of spins. For the latest feat, detailed Monday in the journal Nature Physics, scientists detected the spins of individual atoms.

Researchers combined MRI technology with a scanning tunneling microscope to image a single atom. For the experiment, scientists used a tiny sample of iron and titanium.

Using the atomically sharp metal tip of the microscope, scientists successfully isolated a collection of atoms. Researchers were able to create a three-dimensional map of the atoms' magnetic fields.

Scientists attached another spin cluster to the microscope's tip and passed it over the atomic sample. Like magnets, the spins of the atoms and clusters attracted and repelled each other as the cluster passed from one side to the other. By imaging the magnetic interaction, scientists were able to create an MRI of the individual atoms.

"It turns out that the magnetic interaction we measured depends on the properties of both spins, the one on the tip and the one on the sample," Philip Willke, researcher at the Center for Quantum Nanoscience, QNS, at Ewha Womans University, said in a news release. "For example, the signal that we see for iron atoms is vastly different from that for titanium atoms. This allows us to distinguish different kinds of atoms by their magnetic field signature, and makes our technique very powerful."

In followup experiments, Willke and his colleagues plan to create MRIs of more complex atomic structures, capturing the individual spins that make up molecules and unique magnetic materials.

"Many magnetic phenomena take place on the nanoscale, including the recent generation of magnetic storage devices," said QNS researcher Yujeong Bae. "We now plan to study a variety of systems using our microscopic MRI."

Discoveries made using the new microscopic MRI technology could inspire the creation of new nanomaterials and drugs.

"The ability to map spins and their magnetic fields with previously unimaginable precision allows us to gain deeper knowledge about the structure of matter and opens new fields of basic research," said Andreas Heinrich, director of QNS.

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