Abstract
Atomic scale engineering of magnetic fields is a key ingredient for miniaturizing quantum devices and precision control of quantum systems. This requires a unique combination of magnetic stability and spin-manipulation capabilities. Surface-supported single atom magnets offer such possibilities, where long temporal and thermal stability of the magnetic states can be achieved by maximizing the magnet/ic anisotropy energy (MAE) and by minimizing quantum tunnelling of the magnetization. Here, we show that dysprosium (Dy) atoms on magnesium oxide (MgO) have a giant MAE of 250 meV, currently the highest among all surface spins. Using a variety of scanning tunnelling microscopy (STM) techniques including single atom electron spin resonance (ESR), we confirm no spontaneous spin-switching in Dy over days at ≈ 1 K under low and even vanishing magnetic field. We utilize these robust Dy single atom magnets to engineer magnetic nanostructures, demonstrating unique control of magnetic fields with atomic scale tunability.
Highlights
Atomic scale engineering of magnetic fields is a key ingredient for miniaturizing quantum devices and precision control of quantum systems
Single lanthanide atoms adsorbed on surfaces or incorporated in molecular complexes are being pursued in recent years for applications in quantum information technology and high-density magnetic data storage
Single lanthanide atoms can be directly adsorbed on insulating magnesium oxide (MgO) substrates, and due to the linear bond formed at the oxygen site, large magnet/ic anisotropy energy (MAE) values are expected[12]
Summary
15 2 and configuration a magnetic moment of results in significantly reduced MAE (Fig. S8). For the Fe–Dy pairs the two ESR peaks merge when the external magnetic field compensates the dipolar field from the Dy atom (Bext = −BDy), thereby shifting them with respect to the isolated Fe case (Fig. 3b). Note that we never observe any spin-switching in Dy over days against repeated cycles of Bext ramps within ± 30 mT (see Supplementary section 3), despite an isotopic composition which bears the possibility of spin–flip transitions at low magnetic fields via hyperfine interaction in 161Dy (19% natural abundance) and 163Dy (25% natural abundance) This is in contrast to the case of single Ho atoms on MgO, where spin-switching was observed at slow magnetic field sweeps[16]. Built by positioning one Dy atom at a time at fixed Fe–Dy distance of 1.15 nm (Fig. S6) We prepare their magnetic states into spin down configurations in a site selective manner by injecting high-energy tunnelling electrons (∣Vdc∣ > 150 mV). Interacting Dy spin-centres within a surface-based quantum network can exhibit collective magnetic behaviour with high blocking temperature and slow magnetic relaxation, similar to lanthanide-based single-chain magnets[14,15]
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