![]() Two isotopes have a high nuclear spin and thus display multiple peaks, one peak for each orientation of the nucleus. This is the basis for medical MRI imaging machine, which measures many trillions of nuclear spins for each point in the resulting images.įigure 4: Energy spectra measured on individual titanium atoms. The magnetic field from the nuclear spin is so miniscule that it is difficult to detect, except when many millions are measured at the same time. Only some isotopes have a nucleus with spin, and this spin makes a small magnetic field, just as the earth has a magnetic field due to the electric charge that circulates deep in its core. The magnetism of the nucleus comes from a property called “spin” because it behaves much like a spinning ball of electric charge. The nucleus of an atom is made of protons and neutrons, and the number of protons determines which element the atom is. As a result, two peaks are observed in its energy spectrum, corresponding to the two possible orientations for the spin of the nucleus. ![]() The right atom is the isotope iron-57, which has a nuclear spin. Now, we have extended this to detect the much tinier magnetism of the nucleus.įigure 3: Two iron atoms, seen as blue hills in the lower images, having different isotopes. Three years ago, our group showed that we could detect the magnetism of the electrons of a single atom and use its sensitivity to magnetic fields as a way to detect and measure the properties of nearby magnetic atoms on the surface. We used a scanning tunneling microscope (STM), the Nobel-prize-winning IBM invention that uses the tip of a sharp metal needle to scan a surface to image and move individual atoms with great precision. Working with an international team of collaborators including the Center for Quantum Nanoscience (QNS), the University of Oxford and the International Iberian Nanotechnology Laboratory, we measured iron and titanium atoms that were attached to a carefully prepared surface. The sharp tip of a STM probes a single magnetic atom. Some naturally have a nuclear spin, a small magnet, in their core. Each red ball represents a magnetic atom bonded to a surface.
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